diff --git a/synapse/app/federation_sender.py b/synapse/app/federation_sender.py
index 4f2a9ca21..a08af83a4 100644
--- a/synapse/app/federation_sender.py
+++ b/synapse/app/federation_sender.py
@@ -38,7 +38,7 @@ from synapse.server import HomeServer
 from synapse.storage.engines import create_engine
 from synapse.util.async import Linearizer
 from synapse.util.httpresourcetree import create_resource_tree
-from synapse.util.logcontext import LoggingContext, preserve_fn
+from synapse.util.logcontext import LoggingContext, run_in_background
 from synapse.util.manhole import manhole
 from synapse.util.versionstring import get_version_string
 from twisted.internet import defer, reactor
@@ -229,7 +229,7 @@ class FederationSenderHandler(object):
         # presence, typing, etc.
         if stream_name == "federation":
             send_queue.process_rows_for_federation(self.federation_sender, rows)
-            preserve_fn(self.update_token)(token)
+            run_in_background(self.update_token, token)
 
         # We also need to poke the federation sender when new events happen
         elif stream_name == "events":
diff --git a/synapse/app/pusher.py b/synapse/app/pusher.py
index 739d113ad..26930d1b3 100644
--- a/synapse/app/pusher.py
+++ b/synapse/app/pusher.py
@@ -33,7 +33,7 @@ from synapse.server import HomeServer
 from synapse.storage import DataStore
 from synapse.storage.engines import create_engine
 from synapse.util.httpresourcetree import create_resource_tree
-from synapse.util.logcontext import LoggingContext, preserve_fn
+from synapse.util.logcontext import LoggingContext, run_in_background
 from synapse.util.manhole import manhole
 from synapse.util.versionstring import get_version_string
 from twisted.internet import defer, reactor
@@ -140,7 +140,7 @@ class PusherReplicationHandler(ReplicationClientHandler):
 
     def on_rdata(self, stream_name, token, rows):
         super(PusherReplicationHandler, self).on_rdata(stream_name, token, rows)
-        preserve_fn(self.poke_pushers)(stream_name, token, rows)
+        run_in_background(self.poke_pushers, stream_name, token, rows)
 
     @defer.inlineCallbacks
     def poke_pushers(self, stream_name, token, rows):
diff --git a/synapse/app/synchrotron.py b/synapse/app/synchrotron.py
index 777da564d..7152b1deb 100644
--- a/synapse/app/synchrotron.py
+++ b/synapse/app/synchrotron.py
@@ -51,7 +51,7 @@ from synapse.storage.engines import create_engine
 from synapse.storage.presence import UserPresenceState
 from synapse.storage.roommember import RoomMemberStore
 from synapse.util.httpresourcetree import create_resource_tree
-from synapse.util.logcontext import LoggingContext, preserve_fn
+from synapse.util.logcontext import LoggingContext, run_in_background
 from synapse.util.manhole import manhole
 from synapse.util.stringutils import random_string
 from synapse.util.versionstring import get_version_string
@@ -327,8 +327,7 @@ class SyncReplicationHandler(ReplicationClientHandler):
 
     def on_rdata(self, stream_name, token, rows):
         super(SyncReplicationHandler, self).on_rdata(stream_name, token, rows)
-
-        preserve_fn(self.process_and_notify)(stream_name, token, rows)
+        run_in_background(self.process_and_notify, stream_name, token, rows)
 
     def get_streams_to_replicate(self):
         args = super(SyncReplicationHandler, self).get_streams_to_replicate()
diff --git a/synapse/appservice/scheduler.py b/synapse/appservice/scheduler.py
index dfc8d1b42..6eddbc082 100644
--- a/synapse/appservice/scheduler.py
+++ b/synapse/appservice/scheduler.py
@@ -51,7 +51,7 @@ components.
 from twisted.internet import defer
 
 from synapse.appservice import ApplicationServiceState
-from synapse.util.logcontext import preserve_fn
+from synapse.util.logcontext import run_in_background
 from synapse.util.metrics import Measure
 
 import logging
@@ -106,7 +106,7 @@ class _ServiceQueuer(object):
     def enqueue(self, service, event):
         # if this service isn't being sent something
         self.queued_events.setdefault(service.id, []).append(event)
-        preserve_fn(self._send_request)(service)
+        run_in_background(self._send_request, service)
 
     @defer.inlineCallbacks
     def _send_request(self, service):
@@ -152,10 +152,10 @@ class _TransactionController(object):
                 if sent:
                     yield txn.complete(self.store)
                 else:
-                    preserve_fn(self._start_recoverer)(service)
-        except Exception as e:
-            logger.exception(e)
-            preserve_fn(self._start_recoverer)(service)
+                    run_in_background(self._start_recoverer, service)
+        except Exception:
+            logger.exception("Error creating appservice transaction")
+            run_in_background(self._start_recoverer, service)
 
     @defer.inlineCallbacks
     def on_recovered(self, recoverer):
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index 32b439d20..b748ed2b0 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -281,15 +281,15 @@ class Config(object):
                     )
                 if not cls.path_exists(config_dir_path):
                     os.makedirs(config_dir_path)
-                with open(config_path, "wb") as config_file:
-                    config_bytes, config = obj.generate_config(
+                with open(config_path, "w") as config_file:
+                    config_str, config = obj.generate_config(
                         config_dir_path=config_dir_path,
                         server_name=server_name,
                         report_stats=(config_args.report_stats == "yes"),
                         is_generating_file=True
                     )
                     obj.invoke_all("generate_files", config)
-                    config_file.write(config_bytes)
+                    config_file.write(config_str)
                 print((
                     "A config file has been generated in %r for server name"
                     " %r with corresponding SSL keys and self-signed"
diff --git a/synapse/config/appservice.py b/synapse/config/appservice.py
index 9a2359b6f..277305e18 100644
--- a/synapse/config/appservice.py
+++ b/synapse/config/appservice.py
@@ -17,11 +17,11 @@ from ._base import Config, ConfigError
 from synapse.appservice import ApplicationService
 from synapse.types import UserID
 
-import urllib
 import yaml
 import logging
 
 from six import string_types
+from six.moves.urllib import parse as urlparse
 
 logger = logging.getLogger(__name__)
 
@@ -105,7 +105,7 @@ def _load_appservice(hostname, as_info, config_filename):
         )
 
     localpart = as_info["sender_localpart"]
-    if urllib.quote(localpart) != localpart:
+    if urlparse.quote(localpart) != localpart:
         raise ValueError(
             "sender_localpart needs characters which are not URL encoded."
         )
diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index 3f70039ac..6a7228dc2 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -117,7 +117,7 @@ class LoggingConfig(Config):
         log_config = config.get("log_config")
         if log_config and not os.path.exists(log_config):
             log_file = self.abspath("homeserver.log")
-            with open(log_config, "wb") as log_config_file:
+            with open(log_config, "w") as log_config_file:
                 log_config_file.write(
                     DEFAULT_LOG_CONFIG.substitute(log_file=log_file)
                 )
diff --git a/synapse/config/tls.py b/synapse/config/tls.py
index 29eb012dd..b66154bc7 100644
--- a/synapse/config/tls.py
+++ b/synapse/config/tls.py
@@ -133,7 +133,7 @@ class TlsConfig(Config):
         tls_dh_params_path = config["tls_dh_params_path"]
 
         if not self.path_exists(tls_private_key_path):
-            with open(tls_private_key_path, "w") as private_key_file:
+            with open(tls_private_key_path, "wb") as private_key_file:
                 tls_private_key = crypto.PKey()
                 tls_private_key.generate_key(crypto.TYPE_RSA, 2048)
                 private_key_pem = crypto.dump_privatekey(
@@ -148,7 +148,7 @@ class TlsConfig(Config):
                 )
 
         if not self.path_exists(tls_certificate_path):
-            with open(tls_certificate_path, "w") as certificate_file:
+            with open(tls_certificate_path, "wb") as certificate_file:
                 cert = crypto.X509()
                 subject = cert.get_subject()
                 subject.CN = config["server_name"]
diff --git a/synapse/crypto/keyring.py b/synapse/crypto/keyring.py
index 32cbddbc5..22ee0fc93 100644
--- a/synapse/crypto/keyring.py
+++ b/synapse/crypto/keyring.py
@@ -19,7 +19,8 @@ from synapse.api.errors import SynapseError, Codes
 from synapse.util import unwrapFirstError, logcontext
 from synapse.util.logcontext import (
     PreserveLoggingContext,
-    preserve_fn
+    preserve_fn,
+    run_in_background,
 )
 from synapse.util.metrics import Measure
 
@@ -127,7 +128,7 @@ class Keyring(object):
 
             verify_requests.append(verify_request)
 
-        preserve_fn(self._start_key_lookups)(verify_requests)
+        run_in_background(self._start_key_lookups, verify_requests)
 
         # Pass those keys to handle_key_deferred so that the json object
         # signatures can be verified
@@ -316,7 +317,7 @@ class Keyring(object):
                     if not verify_request.deferred.called:
                         verify_request.deferred.errback(err)
 
-        preserve_fn(do_iterations)().addErrback(on_err)
+        run_in_background(do_iterations).addErrback(on_err)
 
     @defer.inlineCallbacks
     def get_keys_from_store(self, server_name_and_key_ids):
@@ -332,8 +333,9 @@ class Keyring(object):
         """
         res = yield logcontext.make_deferred_yieldable(defer.gatherResults(
             [
-                preserve_fn(self.store.get_server_verify_keys)(
-                    server_name, key_ids
+                run_in_background(
+                    self.store.get_server_verify_keys,
+                    server_name, key_ids,
                 ).addCallback(lambda ks, server: (server, ks), server_name)
                 for server_name, key_ids in server_name_and_key_ids
             ],
@@ -361,7 +363,7 @@ class Keyring(object):
 
         results = yield logcontext.make_deferred_yieldable(defer.gatherResults(
             [
-                preserve_fn(get_key)(p_name, p_keys)
+                run_in_background(get_key, p_name, p_keys)
                 for p_name, p_keys in self.perspective_servers.items()
             ],
             consumeErrors=True,
@@ -401,7 +403,7 @@ class Keyring(object):
 
         results = yield logcontext.make_deferred_yieldable(defer.gatherResults(
             [
-                preserve_fn(get_key)(server_name, key_ids)
+                run_in_background(get_key, server_name, key_ids)
                 for server_name, key_ids in server_name_and_key_ids
             ],
             consumeErrors=True,
@@ -484,7 +486,8 @@ class Keyring(object):
 
         yield logcontext.make_deferred_yieldable(defer.gatherResults(
             [
-                preserve_fn(self.store_keys)(
+                run_in_background(
+                    self.store_keys,
                     server_name=server_name,
                     from_server=perspective_name,
                     verify_keys=response_keys,
@@ -542,7 +545,8 @@ class Keyring(object):
 
         yield logcontext.make_deferred_yieldable(defer.gatherResults(
             [
-                preserve_fn(self.store_keys)(
+                run_in_background(
+                    self.store_keys,
                     server_name=key_server_name,
                     from_server=server_name,
                     verify_keys=verify_keys,
@@ -618,7 +622,8 @@ class Keyring(object):
 
         yield logcontext.make_deferred_yieldable(defer.gatherResults(
             [
-                preserve_fn(self.store.store_server_keys_json)(
+                run_in_background(
+                    self.store.store_server_keys_json,
                     server_name=server_name,
                     key_id=key_id,
                     from_server=server_name,
@@ -719,7 +724,8 @@ class Keyring(object):
         # TODO(markjh): Store whether the keys have expired.
         return logcontext.make_deferred_yieldable(defer.gatherResults(
             [
-                preserve_fn(self.store.store_server_verify_key)(
+                run_in_background(
+                    self.store.store_server_verify_key,
                     server_name, server_name, key.time_added, key
                 )
                 for key_id, key in verify_keys.items()
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index a2067fc39..6163f7c46 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -35,7 +35,7 @@ from synapse.federation.federation_base import (
 import synapse.metrics
 from synapse.util import logcontext, unwrapFirstError
 from synapse.util.caches.expiringcache import ExpiringCache
-from synapse.util.logcontext import make_deferred_yieldable, preserve_fn
+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
 from synapse.util.logutils import log_function
 from synapse.util.retryutils import NotRetryingDestination
 
@@ -419,7 +419,8 @@ class FederationClient(FederationBase):
             batch = set(missing_events[i:i + batch_size])
 
             deferreds = [
-                preserve_fn(self.get_pdu)(
+                run_in_background(
+                    self.get_pdu,
                     destinations=random_server_list(),
                     event_id=e_id,
                 )
diff --git a/synapse/groups/attestations.py b/synapse/groups/attestations.py
index 7187df250..6f11fa374 100644
--- a/synapse/groups/attestations.py
+++ b/synapse/groups/attestations.py
@@ -42,7 +42,7 @@ from twisted.internet import defer
 
 from synapse.api.errors import SynapseError
 from synapse.types import get_domain_from_id
-from synapse.util.logcontext import preserve_fn
+from synapse.util.logcontext import run_in_background
 
 from signedjson.sign import sign_json
 
@@ -196,4 +196,4 @@ class GroupAttestionRenewer(object):
             group_id = row["group_id"]
             user_id = row["user_id"]
 
-            preserve_fn(_renew_attestation)(group_id, user_id)
+            run_in_background(_renew_attestation, group_id, user_id)
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 0245197c0..6cc238830 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -198,7 +198,10 @@ class ApplicationServicesHandler(object):
         services = yield self._get_services_for_3pn(protocol)
 
         results = yield make_deferred_yieldable(defer.DeferredList([
-            preserve_fn(self.appservice_api.query_3pe)(service, kind, protocol, fields)
+            run_in_background(
+                self.appservice_api.query_3pe,
+                service, kind, protocol, fields,
+            )
             for service in services
         ], consumeErrors=True))
 
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index 7eb03ad32..25aec624a 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -24,7 +24,7 @@ from synapse.api.errors import (
     SynapseError, CodeMessageException, FederationDeniedError,
 )
 from synapse.types import get_domain_from_id, UserID
-from synapse.util.logcontext import preserve_fn, make_deferred_yieldable
+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
 from synapse.util.retryutils import NotRetryingDestination
 
 logger = logging.getLogger(__name__)
@@ -139,7 +139,7 @@ class E2eKeysHandler(object):
                 failures[destination] = _exception_to_failure(e)
 
         yield make_deferred_yieldable(defer.gatherResults([
-            preserve_fn(do_remote_query)(destination)
+            run_in_background(do_remote_query, destination)
             for destination in remote_queries_not_in_cache
         ], consumeErrors=True))
 
@@ -242,7 +242,7 @@ class E2eKeysHandler(object):
                 failures[destination] = _exception_to_failure(e)
 
         yield make_deferred_yieldable(defer.gatherResults([
-            preserve_fn(claim_client_keys)(destination)
+            run_in_background(claim_client_keys, destination)
             for destination in remote_queries
         ], consumeErrors=True))
 
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 260df025f..bab0db290 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -639,7 +639,8 @@ class FederationHandler(BaseHandler):
 
                 results = yield logcontext.make_deferred_yieldable(defer.gatherResults(
                     [
-                        logcontext.preserve_fn(self.replication_layer.get_pdu)(
+                        logcontext.run_in_background(
+                            self.replication_layer.get_pdu,
                             [dest],
                             event_id,
                             outlier=True,
@@ -1025,7 +1026,7 @@ class FederationHandler(BaseHandler):
             # lots of requests for missing prev_events which we do actually
             # have. Hence we fire off the deferred, but don't wait for it.
 
-            logcontext.preserve_fn(self._handle_queued_pdus)(room_queue)
+            logcontext.run_in_background(self._handle_queued_pdus, room_queue)
 
         defer.returnValue(True)
 
@@ -1527,8 +1528,9 @@ class FederationHandler(BaseHandler):
         if not backfilled:
             # this intentionally does not yield: we don't care about the result
             # and don't need to wait for it.
-            logcontext.preserve_fn(self.pusher_pool.on_new_notifications)(
-                event_stream_id, max_stream_id
+            logcontext.run_in_background(
+                self.pusher_pool.on_new_notifications,
+                event_stream_id, max_stream_id,
             )
 
         defer.returnValue((context, event_stream_id, max_stream_id))
@@ -1542,7 +1544,8 @@ class FederationHandler(BaseHandler):
         """
         contexts = yield logcontext.make_deferred_yieldable(defer.gatherResults(
             [
-                logcontext.preserve_fn(self._prep_event)(
+                logcontext.run_in_background(
+                    self._prep_event,
                     origin,
                     ev_info["event"],
                     state=ev_info.get("state"),
@@ -1871,7 +1874,8 @@ class FederationHandler(BaseHandler):
 
             different_events = yield logcontext.make_deferred_yieldable(
                 defer.gatherResults([
-                    logcontext.preserve_fn(self.store.get_event)(
+                    logcontext.run_in_background(
+                        self.store.get_event,
                         d,
                         allow_none=True,
                         allow_rejected=False,
diff --git a/synapse/handlers/initial_sync.py b/synapse/handlers/initial_sync.py
index c5267b4b8..cd33a8659 100644
--- a/synapse/handlers/initial_sync.py
+++ b/synapse/handlers/initial_sync.py
@@ -27,7 +27,7 @@ from synapse.types import (
 from synapse.util import unwrapFirstError
 from synapse.util.async import concurrently_execute
 from synapse.util.caches.snapshot_cache import SnapshotCache
-from synapse.util.logcontext import make_deferred_yieldable, preserve_fn
+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
 from synapse.visibility import filter_events_for_client
 
 from ._base import BaseHandler
@@ -166,7 +166,8 @@ class InitialSyncHandler(BaseHandler):
                 (messages, token), current_state = yield make_deferred_yieldable(
                     defer.gatherResults(
                         [
-                            preserve_fn(self.store.get_recent_events_for_room)(
+                            run_in_background(
+                                self.store.get_recent_events_for_room,
                                 event.room_id,
                                 limit=limit,
                                 end_token=room_end_token,
@@ -391,9 +392,10 @@ class InitialSyncHandler(BaseHandler):
 
         presence, receipts, (messages, token) = yield defer.gatherResults(
             [
-                preserve_fn(get_presence)(),
-                preserve_fn(get_receipts)(),
-                preserve_fn(self.store.get_recent_events_for_room)(
+                run_in_background(get_presence),
+                run_in_background(get_receipts),
+                run_in_background(
+                    self.store.get_recent_events_for_room,
                     room_id,
                     limit=limit,
                     end_token=now_token.room_key,
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index ad932bdd9..23502eda7 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -31,7 +31,7 @@ from synapse.types import (
     UserID, RoomAlias, RoomStreamToken,
 )
 from synapse.util.async import run_on_reactor, ReadWriteLock, Limiter
-from synapse.util.logcontext import preserve_fn, run_in_background
+from synapse.util.logcontext import run_in_background
 from synapse.util.metrics import measure_func
 from synapse.util.frozenutils import frozendict_json_encoder
 from synapse.util.stringutils import random_string
@@ -857,7 +857,8 @@ class EventCreationHandler(object):
 
         # this intentionally does not yield: we don't care about the result
         # and don't need to wait for it.
-        preserve_fn(self.pusher_pool.on_new_notifications)(
+        run_in_background(
+            self.pusher_pool.on_new_notifications,
             event_stream_id, max_stream_id
         )
 
@@ -872,7 +873,7 @@ class EventCreationHandler(object):
             except Exception:
                 logger.exception("Error notifying about new room event")
 
-        preserve_fn(_notify)()
+        run_in_background(_notify)
 
         if event.type == EventTypes.Message:
             # We don't want to block sending messages on any presence code. This
diff --git a/synapse/handlers/typing.py b/synapse/handlers/typing.py
index 823e2e27e..5d9736e88 100644
--- a/synapse/handlers/typing.py
+++ b/synapse/handlers/typing.py
@@ -16,7 +16,7 @@
 from twisted.internet import defer
 
 from synapse.api.errors import SynapseError, AuthError
-from synapse.util.logcontext import preserve_fn
+from synapse.util.logcontext import run_in_background
 from synapse.util.metrics import Measure
 from synapse.util.wheel_timer import WheelTimer
 from synapse.types import UserID, get_domain_from_id
@@ -97,7 +97,8 @@ class TypingHandler(object):
             if self.hs.is_mine_id(member.user_id):
                 last_fed_poke = self._member_last_federation_poke.get(member, None)
                 if not last_fed_poke or last_fed_poke + FEDERATION_PING_INTERVAL <= now:
-                    preserve_fn(self._push_remote)(
+                    run_in_background(
+                        self._push_remote,
                         member=member,
                         typing=True
                     )
@@ -196,7 +197,7 @@ class TypingHandler(object):
     def _push_update(self, member, typing):
         if self.hs.is_mine_id(member.user_id):
             # Only send updates for changes to our own users.
-            preserve_fn(self._push_remote)(member, typing)
+            run_in_background(self._push_remote, member, typing)
 
         self._push_update_local(
             member=member,
diff --git a/synapse/http/client.py b/synapse/http/client.py
index 62309c336..70a19d9b7 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -40,7 +40,7 @@ from twisted.web.http import PotentialDataLoss
 from twisted.web.http_headers import Headers
 from twisted.web._newclient import ResponseDone
 
-from StringIO import StringIO
+from six import StringIO
 
 import simplejson as json
 import logging
@@ -507,7 +507,7 @@ class SpiderHttpClient(SimpleHttpClient):
                     reactor,
                     SpiderEndpointFactory(hs)
                 )
-            ), [('gzip', GzipDecoder)]
+            ), [(b'gzip', GzipDecoder)]
         )
         # We could look like Chrome:
         # self.user_agent = ("Mozilla/5.0 (%s) (KHTML, like Gecko)
diff --git a/synapse/http/endpoint.py b/synapse/http/endpoint.py
index 00572c289..db455e590 100644
--- a/synapse/http/endpoint.py
+++ b/synapse/http/endpoint.py
@@ -286,7 +286,7 @@ def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=t
         if (len(answers) == 1
                 and answers[0].type == dns.SRV
                 and answers[0].payload
-                and answers[0].payload.target == dns.Name('.')):
+                and answers[0].payload.target == dns.Name(b'.')):
             raise ConnectError("Service %s unavailable" % service_name)
 
         for answer in answers:
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 30036fe81..4b2b85464 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -41,8 +41,7 @@ import logging
 import random
 import sys
 import urllib
-import urlparse
-
+from six.moves.urllib import parse as urlparse
 
 logger = logging.getLogger(__name__)
 outbound_logger = logging.getLogger("synapse.http.outbound")
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 8d632290d..55b9ad525 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -546,6 +546,6 @@ def _request_user_agent_is_curl(request):
         b"User-Agent", default=[]
     )
     for user_agent in user_agents:
-        if "curl" in user_agent:
+        if b"curl" in user_agent:
             return True
     return False
diff --git a/synapse/push/pusherpool.py b/synapse/push/pusherpool.py
index 2f467d1f9..750d11ca3 100644
--- a/synapse/push/pusherpool.py
+++ b/synapse/push/pusherpool.py
@@ -14,13 +14,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import logging
+
 from twisted.internet import defer
 
-from .pusher import PusherFactory
-from synapse.util.logcontext import make_deferred_yieldable, preserve_fn
+from synapse.push.pusher import PusherFactory
 from synapse.util.async import run_on_reactor
-
-import logging
+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
 
 logger = logging.getLogger(__name__)
 
@@ -137,8 +137,9 @@ class PusherPool:
                 if u in self.pushers:
                     for p in self.pushers[u].values():
                         deferreds.append(
-                            preserve_fn(p.on_new_notifications)(
-                                min_stream_id, max_stream_id
+                            run_in_background(
+                                p.on_new_notifications,
+                                min_stream_id, max_stream_id,
                             )
                         )
 
@@ -166,7 +167,10 @@ class PusherPool:
                 if u in self.pushers:
                     for p in self.pushers[u].values():
                         deferreds.append(
-                            preserve_fn(p.on_new_receipts)(min_stream_id, max_stream_id)
+                            run_in_background(
+                                p.on_new_receipts,
+                                min_stream_id, max_stream_id,
+                            )
                         )
 
             yield make_deferred_yieldable(
@@ -211,7 +215,7 @@ class PusherPool:
                 if appid_pushkey in byuser:
                     byuser[appid_pushkey].on_stop()
                 byuser[appid_pushkey] = p
-                preserve_fn(p.on_started)()
+                run_in_background(p.on_started)
 
         logger.info("Started pushers")
 
diff --git a/synapse/rest/client/v1/login.py b/synapse/rest/client/v1/login.py
index 45844aa2d..34df5be4e 100644
--- a/synapse/rest/client/v1/login.py
+++ b/synapse/rest/client/v1/login.py
@@ -25,7 +25,7 @@ from .base import ClientV1RestServlet, client_path_patterns
 
 import simplejson as json
 import urllib
-import urlparse
+from six.moves.urllib import parse as urlparse
 
 import logging
 from saml2 import BINDING_HTTP_POST
diff --git a/synapse/rest/client/v1/register.py b/synapse/rest/client/v1/register.py
index 8a8209717..9b3022e0b 100644
--- a/synapse/rest/client/v1/register.py
+++ b/synapse/rest/client/v1/register.py
@@ -30,6 +30,8 @@ from hashlib import sha1
 import hmac
 import logging
 
+from six import string_types
+
 logger = logging.getLogger(__name__)
 
 
@@ -333,11 +335,11 @@ class RegisterRestServlet(ClientV1RestServlet):
     def _do_shared_secret(self, request, register_json, session):
         yield run_on_reactor()
 
-        if not isinstance(register_json.get("mac", None), basestring):
+        if not isinstance(register_json.get("mac", None), string_types):
             raise SynapseError(400, "Expected mac.")
-        if not isinstance(register_json.get("user", None), basestring):
+        if not isinstance(register_json.get("user", None), string_types):
             raise SynapseError(400, "Expected 'user' key.")
-        if not isinstance(register_json.get("password", None), basestring):
+        if not isinstance(register_json.get("password", None), string_types):
             raise SynapseError(400, "Expected 'password' key.")
 
         if not self.hs.config.registration_shared_secret:
@@ -358,14 +360,14 @@ class RegisterRestServlet(ClientV1RestServlet):
         got_mac = str(register_json["mac"])
 
         want_mac = hmac.new(
-            key=self.hs.config.registration_shared_secret,
+            key=self.hs.config.registration_shared_secret.encode(),
             digestmod=sha1,
         )
         want_mac.update(user)
-        want_mac.update("\x00")
+        want_mac.update(b"\x00")
         want_mac.update(password)
-        want_mac.update("\x00")
-        want_mac.update("admin" if admin else "notadmin")
+        want_mac.update(b"\x00")
+        want_mac.update(b"admin" if admin else b"notadmin")
         want_mac = want_mac.hexdigest()
 
         if compare_digest(want_mac, got_mac):
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 2ad0e5943..fcf9c9ab4 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -28,8 +28,9 @@ from synapse.http.servlet import (
     parse_json_object_from_request, parse_string, parse_integer
 )
 
+from six.moves.urllib import parse as urlparse
+
 import logging
-import urllib
 import simplejson as json
 
 logger = logging.getLogger(__name__)
@@ -433,7 +434,7 @@ class RoomMessageListRestServlet(ClientV1RestServlet):
         as_client_event = "raw" not in request.args
         filter_bytes = request.args.get("filter", None)
         if filter_bytes:
-            filter_json = urllib.unquote(filter_bytes[-1]).decode("UTF-8")
+            filter_json = urlparse.unquote(filter_bytes[-1]).decode("UTF-8")
             event_filter = Filter(json.loads(filter_json))
         else:
             event_filter = None
@@ -718,8 +719,8 @@ class RoomTypingRestServlet(ClientV1RestServlet):
     def on_PUT(self, request, room_id, user_id):
         requester = yield self.auth.get_user_by_req(request)
 
-        room_id = urllib.unquote(room_id)
-        target_user = UserID.from_string(urllib.unquote(user_id))
+        room_id = urlparse.unquote(room_id)
+        target_user = UserID.from_string(urlparse.unquote(user_id))
 
         content = parse_json_object_from_request(request)
 
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index f317c919d..5cab00aea 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -35,6 +35,8 @@ from hashlib import sha1
 from synapse.util.async import run_on_reactor
 from synapse.util.ratelimitutils import FederationRateLimiter
 
+from six import string_types
+
 
 # We ought to be using hmac.compare_digest() but on older pythons it doesn't
 # exist. It's a _really minor_ security flaw to use plain string comparison
@@ -210,14 +212,14 @@ class RegisterRestServlet(RestServlet):
         # in sessions. Pull out the username/password provided to us.
         desired_password = None
         if 'password' in body:
-            if (not isinstance(body['password'], basestring) or
+            if (not isinstance(body['password'], string_types) or
                     len(body['password']) > 512):
                 raise SynapseError(400, "Invalid password")
             desired_password = body["password"]
 
         desired_username = None
         if 'username' in body:
-            if (not isinstance(body['username'], basestring) or
+            if (not isinstance(body['username'], string_types) or
                     len(body['username']) > 512):
                 raise SynapseError(400, "Invalid username")
             desired_username = body['username']
@@ -243,7 +245,7 @@ class RegisterRestServlet(RestServlet):
 
             access_token = get_access_token_from_request(request)
 
-            if isinstance(desired_username, basestring):
+            if isinstance(desired_username, string_types):
                 result = yield self._do_appservice_registration(
                     desired_username, access_token, body
                 )
@@ -464,7 +466,7 @@ class RegisterRestServlet(RestServlet):
         # includes the password and admin flag in the hashed text. Why are
         # these different?
         want_mac = hmac.new(
-            key=self.hs.config.registration_shared_secret,
+            key=self.hs.config.registration_shared_secret.encode(),
             msg=user,
             digestmod=sha1,
         ).hexdigest()
diff --git a/synapse/rest/media/v1/_base.py b/synapse/rest/media/v1/_base.py
index e7ac01da0..d9c4af938 100644
--- a/synapse/rest/media/v1/_base.py
+++ b/synapse/rest/media/v1/_base.py
@@ -28,7 +28,7 @@ import os
 
 import logging
 import urllib
-import urlparse
+from six.moves.urllib import parse as urlparse
 
 logger = logging.getLogger(__name__)
 
diff --git a/synapse/rest/media/v1/media_repository.py b/synapse/rest/media/v1/media_repository.py
index bb7959937..9800ce758 100644
--- a/synapse/rest/media/v1/media_repository.py
+++ b/synapse/rest/media/v1/media_repository.py
@@ -47,7 +47,7 @@ import shutil
 
 import cgi
 import logging
-import urlparse
+from six.moves.urllib import parse as urlparse
 
 logger = logging.getLogger(__name__)
 
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 0fc21540c..9290d7946 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -35,7 +35,7 @@ from ._base import FileInfo
 from synapse.api.errors import (
     SynapseError, Codes,
 )
-from synapse.util.logcontext import preserve_fn, make_deferred_yieldable
+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
 from synapse.util.stringutils import random_string
 from synapse.util.caches.expiringcache import ExpiringCache
 from synapse.http.client import SpiderHttpClient
@@ -144,7 +144,8 @@ class PreviewUrlResource(Resource):
         observable = self._cache.get(url)
 
         if not observable:
-            download = preserve_fn(self._do_preview)(
+            download = run_in_background(
+                self._do_preview,
                 url, requester.user, ts,
             )
             observable = ObservableDeferred(
diff --git a/synapse/rest/media/v1/upload_resource.py b/synapse/rest/media/v1/upload_resource.py
index f6f498cdc..a31e75cb4 100644
--- a/synapse/rest/media/v1/upload_resource.py
+++ b/synapse/rest/media/v1/upload_resource.py
@@ -81,15 +81,15 @@ class UploadResource(Resource):
         headers = request.requestHeaders
 
         if headers.hasHeader("Content-Type"):
-            media_type = headers.getRawHeaders("Content-Type")[0]
+            media_type = headers.getRawHeaders(b"Content-Type")[0]
         else:
             raise SynapseError(
                 msg="Upload request missing 'Content-Type'",
                 code=400,
             )
 
-        # if headers.hasHeader("Content-Disposition"):
-        #     disposition = headers.getRawHeaders("Content-Disposition")[0]
+        # if headers.hasHeader(b"Content-Disposition"):
+        #     disposition = headers.getRawHeaders(b"Content-Disposition")[0]
         # TODO(markjh): parse content-dispostion
 
         content_uri = yield self.media_repo.create_content(
diff --git a/synapse/storage/events_worker.py b/synapse/storage/events_worker.py
index a937b9bce..ba834854e 100644
--- a/synapse/storage/events_worker.py
+++ b/synapse/storage/events_worker.py
@@ -20,7 +20,7 @@ from synapse.events import FrozenEvent
 from synapse.events.utils import prune_event
 
 from synapse.util.logcontext import (
-    preserve_fn, PreserveLoggingContext, make_deferred_yieldable
+    PreserveLoggingContext, make_deferred_yieldable, run_in_background,
 )
 from synapse.util.metrics import Measure
 from synapse.api.errors import SynapseError
@@ -319,7 +319,8 @@ class EventsWorkerStore(SQLBaseStore):
 
         res = yield make_deferred_yieldable(defer.gatherResults(
             [
-                preserve_fn(self._get_event_from_row)(
+                run_in_background(
+                    self._get_event_from_row,
                     row["internal_metadata"], row["json"], row["redacts"],
                     rejected_reason=row["rejects"],
                 )
diff --git a/synapse/storage/stream.py b/synapse/storage/stream.py
index 52c90d8e0..f0784ba13 100644
--- a/synapse/storage/stream.py
+++ b/synapse/storage/stream.py
@@ -41,7 +41,7 @@ from synapse.storage.events import EventsWorkerStore
 from synapse.util.caches.descriptors import cached
 from synapse.types import RoomStreamToken
 from synapse.util.caches.stream_change_cache import StreamChangeCache
-from synapse.util.logcontext import make_deferred_yieldable, preserve_fn
+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 
 import abc
@@ -200,7 +200,8 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
         room_ids = list(room_ids)
         for rm_ids in (room_ids[i:i + 20] for i in range(0, len(room_ids), 20)):
             res = yield make_deferred_yieldable(defer.gatherResults([
-                preserve_fn(self.get_room_events_stream_for_room)(
+                run_in_background(
+                    self.get_room_events_stream_for_room,
                     room_id, from_key, to_key, limit, order=order,
                 )
                 for room_id in rm_ids
diff --git a/synapse/util/async.py b/synapse/util/async.py
index cb53c3112..9dd4e6b5b 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -19,7 +19,7 @@ from twisted.internet.defer import CancelledError
 from twisted.python import failure
 
 from .logcontext import (
-    PreserveLoggingContext, make_deferred_yieldable, preserve_fn
+    PreserveLoggingContext, make_deferred_yieldable, run_in_background
 )
 from synapse.util import logcontext, unwrapFirstError
 
@@ -165,7 +165,7 @@ def concurrently_execute(func, args, limit):
             pass
 
     return logcontext.make_deferred_yieldable(defer.gatherResults([
-        preserve_fn(_concurrently_execute_inner)()
+        run_in_background(_concurrently_execute_inner)
         for _ in range(limit)
     ], consumeErrors=True)).addErrback(unwrapFirstError)
 
diff --git a/synapse/util/file_consumer.py b/synapse/util/file_consumer.py
index 3c8a16533..3380970e4 100644
--- a/synapse/util/file_consumer.py
+++ b/synapse/util/file_consumer.py
@@ -15,7 +15,7 @@
 
 from twisted.internet import threads, reactor
 
-from synapse.util.logcontext import make_deferred_yieldable, preserve_fn
+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
 
 from six.moves import queue
 
@@ -70,7 +70,9 @@ class BackgroundFileConsumer(object):
 
         self._producer = producer
         self.streaming = streaming
-        self._finished_deferred = preserve_fn(threads.deferToThread)(self._writer)
+        self._finished_deferred = run_in_background(
+            threads.deferToThread, self._writer
+        )
         if not streaming:
             self._producer.resumeProducing()
 
diff --git a/synapse/util/httpresourcetree.py b/synapse/util/httpresourcetree.py
index d74784955..e9f0f292e 100644
--- a/synapse/util/httpresourcetree.py
+++ b/synapse/util/httpresourcetree.py
@@ -40,9 +40,12 @@ def create_resource_tree(desired_tree, root_resource):
     # extra resources to existing nodes. See self._resource_id for the key.
     resource_mappings = {}
     for full_path, res in desired_tree.items():
+        # twisted requires all resources to be bytes
+        full_path = full_path.encode("utf-8")
+
         logger.info("Attaching %s to path %s", res, full_path)
         last_resource = root_resource
-        for path_seg in full_path.split('/')[1:-1]:
+        for path_seg in full_path.split(b'/')[1:-1]:
             if path_seg not in last_resource.listNames():
                 # resource doesn't exist, so make a "dummy resource"
                 child_resource = NoResource()
@@ -57,7 +60,7 @@ def create_resource_tree(desired_tree, root_resource):
 
         # ===========================
         # now attach the actual desired resource
-        last_path_seg = full_path.split('/')[-1]
+        last_path_seg = full_path.split(b'/')[-1]
 
         # if there is already a resource here, thieve its children and
         # replace it
diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py
index d6587e440..bbadeec92 100644
--- a/synapse/util/logcontext.py
+++ b/synapse/util/logcontext.py
@@ -346,7 +346,7 @@ def make_deferred_yieldable(deferred):
     returning a deferred. Then, when the deferred completes, restores the
     current logcontext before running callbacks/errbacks.
 
-    (This is more-or-less the opposite operation to preserve_fn.)
+    (This is more-or-less the opposite operation to run_in_background.)
     """
     if isinstance(deferred, defer.Deferred) and not deferred.called:
         prev_context = LoggingContext.set_current_context(LoggingContext.sentinel)
diff --git a/synapse/util/logformatter.py b/synapse/util/logformatter.py
index cdbc4bffd..59ab3c696 100644
--- a/synapse/util/logformatter.py
+++ b/synapse/util/logformatter.py
@@ -14,7 +14,7 @@
 # limitations under the License.
 
 
-import StringIO
+from six import StringIO
 import logging
 import traceback
 
diff --git a/synapse/util/ratelimitutils.py b/synapse/util/ratelimitutils.py
index 1101881a2..18424f6c3 100644
--- a/synapse/util/ratelimitutils.py
+++ b/synapse/util/ratelimitutils.py
@@ -18,7 +18,7 @@ from twisted.internet import defer
 from synapse.api.errors import LimitExceededError
 
 from synapse.util.async import sleep
-from synapse.util.logcontext import preserve_fn
+from synapse.util.logcontext import run_in_background
 
 import collections
 import contextlib
@@ -150,7 +150,7 @@ class _PerHostRatelimiter(object):
                 "Ratelimit [%s]: sleeping req",
                 id(request_id),
             )
-            ret_defer = preserve_fn(sleep)(self.sleep_msec / 1000.0)
+            ret_defer = run_in_background(sleep, self.sleep_msec / 1000.0)
 
             self.sleeping_requests.add(request_id)
 
diff --git a/synapse/util/retryutils.py b/synapse/util/retryutils.py
index 47b0bb5eb..4e93f69d3 100644
--- a/synapse/util/retryutils.py
+++ b/synapse/util/retryutils.py
@@ -203,8 +203,8 @@ class RetryDestinationLimiter(object):
                 )
             except Exception:
                 logger.exception(
-                    "Failed to store set_destination_retry_timings",
+                    "Failed to store destination_retry_timings",
                 )
 
         # we deliberately do this in the background.
-        synapse.util.logcontext.preserve_fn(store_retry_timings)()
+        synapse.util.logcontext.run_in_background(store_retry_timings)
diff --git a/tests/rest/client/v1/test_rooms.py b/tests/rest/client/v1/test_rooms.py
index 7e8966a1a..d763400ea 100644
--- a/tests/rest/client/v1/test_rooms.py
+++ b/tests/rest/client/v1/test_rooms.py
@@ -24,7 +24,7 @@ from synapse.api.constants import Membership
 from synapse.types import UserID
 
 import json
-import urllib
+from six.moves.urllib import parse as urlparse
 
 from ....utils import MockHttpResource, setup_test_homeserver
 from .utils import RestTestCase
@@ -766,7 +766,7 @@ class RoomMemberStateTestCase(RestTestCase):
     @defer.inlineCallbacks
     def test_rooms_members_self(self):
         path = "/rooms/%s/state/m.room.member/%s" % (
-            urllib.quote(self.room_id), self.user_id
+            urlparse.quote(self.room_id), self.user_id
         )
 
         # valid join message (NOOP since we made the room)
@@ -786,7 +786,7 @@ class RoomMemberStateTestCase(RestTestCase):
     def test_rooms_members_other(self):
         self.other_id = "@zzsid1:red"
         path = "/rooms/%s/state/m.room.member/%s" % (
-            urllib.quote(self.room_id), self.other_id
+            urlparse.quote(self.room_id), self.other_id
         )
 
         # valid invite message
@@ -802,7 +802,7 @@ class RoomMemberStateTestCase(RestTestCase):
     def test_rooms_members_other_custom_keys(self):
         self.other_id = "@zzsid1:red"
         path = "/rooms/%s/state/m.room.member/%s" % (
-            urllib.quote(self.room_id), self.other_id
+            urlparse.quote(self.room_id), self.other_id
         )
 
         # valid invite message with custom key
@@ -859,7 +859,7 @@ class RoomMessagesTestCase(RestTestCase):
     @defer.inlineCallbacks
     def test_invalid_puts(self):
         path = "/rooms/%s/send/m.room.message/mid1" % (
-            urllib.quote(self.room_id))
+            urlparse.quote(self.room_id))
         # missing keys or invalid json
         (code, response) = yield self.mock_resource.trigger(
             "PUT", path, '{}'
@@ -894,7 +894,7 @@ class RoomMessagesTestCase(RestTestCase):
     @defer.inlineCallbacks
     def test_rooms_messages_sent(self):
         path = "/rooms/%s/send/m.room.message/mid1" % (
-            urllib.quote(self.room_id))
+            urlparse.quote(self.room_id))
 
         content = '{"body":"test","msgtype":{"type":"a"}}'
         (code, response) = yield self.mock_resource.trigger("PUT", path, content)
@@ -911,7 +911,7 @@ class RoomMessagesTestCase(RestTestCase):
 
         # m.text message type
         path = "/rooms/%s/send/m.room.message/mid2" % (
-            urllib.quote(self.room_id))
+            urlparse.quote(self.room_id))
         content = '{"body":"test2","msgtype":"m.text"}'
         (code, response) = yield self.mock_resource.trigger("PUT", path, content)
         self.assertEquals(200, code, msg=str(response))
diff --git a/tests/utils.py b/tests/utils.py
index 0cd9f7eee..c2beb5d9f 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -15,8 +15,7 @@
 
 import hashlib
 from inspect import getcallargs
-import urllib
-import urlparse
+from six.moves.urllib import parse as urlparse
 
 from mock import Mock, patch
 from twisted.internet import defer, reactor
@@ -238,7 +237,7 @@ class MockHttpResource(HttpServer):
             if matcher:
                 try:
                     args = [
-                        urllib.unquote(u).decode("UTF-8")
+                        urlparse.unquote(u).decode("UTF-8")
                         for u in matcher.groups()
                     ]
 
diff --git a/tox.ini b/tox.ini
index f408defc8..ca8373662 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = packaging, py27, pep8
+envlist = packaging, py27, py36, pep8
 
 [testenv]
 deps =
@@ -46,6 +46,14 @@ commands =
 # )
 usedevelop=true
 
+[testenv:py36]
+usedevelop=true
+commands =
+    /usr/bin/find "{toxinidir}" -name '*.pyc' -delete
+    coverage run {env:COVERAGE_OPTS:} --source="{toxinidir}/synapse" \
+        "{envbindir}/trial" {env:TRIAL_FLAGS:} {posargs:tests/metrics} {env:TOXSUFFIX:}
+    {env:DUMP_COVERAGE_COMMAND:coverage report -m}
+
 [testenv:packaging]
 deps =
     check-manifest