Remote dependency on distutils (#9125)

`distutils` is pretty much deprecated these days, and replaced with
`setuptools`. It's also annoying because it's you can't `pip install` it, and
it's hard to figure out which debian package we should depend on to make sure
it's there.

Since we only use it for a tiny function anyway, let's just vendor said
function into our codebase.

changelog.d/9125.misc

@@ -0,0 +1 @@
+Remove dependency on `distutils`.

debian/changelog

@@ -1,3 +1,9 @@
+matrix-synapse-py3 (1.25.0ubuntu1) UNRELEASED; urgency=medium
+
+  * Remove dependency on `python3-distutils`.
+
+ -- Richard van der Hoff <richard@matrix.org>  Fri, 15 Jan 2021 12:44:19 +0000
+
 matrix-synapse-py3 (1.25.0) stable; urgency=medium
 
   [ Dan Callahan ]

debian/control

@@ -31,7 +31,6 @@ Pre-Depends: dpkg (>= 1.16.1)
 Depends:
  adduser,
  debconf,
- python3-distutils|libpython3-stdlib (<< 3.6),
  ${misc:Depends},
  ${shlibs:Depends},
  ${synapse:pydepends},

synapse/config/registration.py

@@ -14,14 +14,13 @@
 # limitations under the License.
 
 import os
-from distutils.util import strtobool
 
 import pkg_resources
 
 from synapse.api.constants import RoomCreationPreset
 from synapse.config._base import Config, ConfigError
 from synapse.types import RoomAlias, UserID
-from synapse.util.stringutils import random_string_with_symbols
+from synapse.util.stringutils import random_string_with_symbols, strtobool
 
 
 class AccountValidityConfig(Config):
@@ -86,12 +85,12 @@ class RegistrationConfig(Config):
     section = "registration"
 
     def read_config(self, config, **kwargs):
-        self.enable_registration = bool(
-            strtobool(str(config.get("enable_registration", False)))
+        self.enable_registration = strtobool(
+            str(config.get("enable_registration", False))
         )
         if "disable_registration" in config:
-            self.enable_registration = not bool(
-                strtobool(str(config["disable_registration"]))
+            self.enable_registration = not strtobool(
+                str(config["disable_registration"])
             )
 
         self.account_validity = AccountValidityConfig(

synapse/events/__init__.py

@@ -17,7 +17,6 @@
 
 import abc
 import os
-from distutils.util import strtobool
 from typing import Dict, Optional, Tuple, Type
 
 from unpaddedbase64 import encode_base64
@@ -26,6 +25,7 @@ from synapse.api.room_versions import EventFormatVersions, RoomVersion, RoomVers
 from synapse.types import JsonDict, RoomStreamToken
 from synapse.util.caches import intern_dict
 from synapse.util.frozenutils import freeze
+from synapse.util.stringutils import strtobool
 
 # Whether we should use frozen_dict in FrozenEvent. Using frozen_dicts prevents
 # bugs where we accidentally share e.g. signature dicts. However, converting a
@@ -34,6 +34,7 @@ from synapse.util.frozenutils import freeze
 # NOTE: This is overridden by the configuration by the Synapse worker apps, but
 # for the sake of tests, it is set here while it cannot be configured on the
 # homeserver object itself.
+
 USE_FROZEN_DICTS = strtobool(os.environ.get("SYNAPSE_USE_FROZEN_DICTS", "0"))
 
 

synapse/util/stringutils.py

@@ -75,3 +75,22 @@ def shortstr(iterable: Iterable, maxitems: int = 5) -> str:
     if len(items) <= maxitems:
         return str(items)
     return "[" + ", ".join(repr(r) for r in items[:maxitems]) + ", ...]"
+
+
+def strtobool(val: str) -> bool:
+    """Convert a string representation of truth to True or False
+
+    True values are 'y', 'yes', 't', 'true', 'on', and '1'; false values
+    are 'n', 'no', 'f', 'false', 'off', and '0'.  Raises ValueError if
+    'val' is anything else.
+
+    This is lifted from distutils.util.strtobool, with the exception that it actually
+    returns a bool, rather than an int.
+    """
+    val = val.lower()
+    if val in ("y", "yes", "t", "true", "on", "1"):
+        return True
+    elif val in ("n", "no", "f", "false", "off", "0"):
+        return False
+    else:
+        raise ValueError("invalid truth value %r" % (val,))