Modify API for SimpleHttpClient.get_json and update usages.

Previously, this would only return the HTTP body as JSON, and discard other
response information (e.g. the HTTP response code). This has now been changed
to throw a CodeMessageException on a non-2xx response, with the response code
and body, which can then be parsed as JSON.

Affected modules include:
 - Registration/Login (when using an email for IS auth)

synapse/handlers/login.py

@@ -16,12 +16,13 @@
 from twisted.internet import defer
 
 from ._base import BaseHandler
-from synapse.api.errors import LoginError, Codes
+from synapse.api.errors import LoginError, Codes, CodeMessageException
 from synapse.http.client import SimpleHttpClient
 from synapse.util.emailutils import EmailException
 import synapse.util.emailutils as emailutils
 
 import bcrypt
+import json
 import logging
 
 logger = logging.getLogger(__name__)
@@ -96,16 +97,20 @@ class LoginHandler(BaseHandler):
 
     @defer.inlineCallbacks
     def _query_email(self, email):
-        httpCli = SimpleHttpClient(self.hs)
-        data = yield httpCli.get_json(
-            # TODO FIXME This should be configurable.
-            # XXX: ID servers need to use HTTPS
-            "http://%s%s" % (
-                "matrix.org:8090", "/_matrix/identity/api/v1/lookup"
-            ),
-            {
-                'medium': 'email',
-                'address': email
-            }
-        )
-        defer.returnValue(data)
+        http_client = SimpleHttpClient(self.hs)
+        try:
+            data = yield http_client.get_json(
+                # TODO FIXME This should be configurable.
+                # XXX: ID servers need to use HTTPS
+                "http://%s%s" % (
+                    "matrix.org:8090", "/_matrix/identity/api/v1/lookup"
+                ),
+                {
+                    'medium': 'email',
+                    'address': email
+                }
+            )
+            defer.returnValue(data)
+        except CodeMessageException as e:
+            data = json.loads(e.msg)
+            defer.returnValue(data)