Missing cgi module in Python 3.13

[arkamar]

Description

It seems all synapse dependencies now support Python 3.13 (at least in Gentoo), therefore I tried to run synapse tests in Py3.13 environment. Tests fail because the cgi module was removed from Py3.13. See the error log below.

Steps to reproduce

• prepare Py3.13 env
• run tests

Homeserver

homeserver

Synapse Version

1.115.0

Installation Method

Other (please mention below)

Database

sqlite

Workers

Single process

Platform

Gentoo amd64 in docker container.

Configuration

No response

Relevant log output

[ERROR]
Traceback (most recent call last):
  File "/usr/lib/python3.13/site-packages/twisted/trial/runner.py", line 711, in loadByName
    return self.suiteFactory([self.findByName(name, recurse=recurse)])
  File "/usr/lib/python3.13/site-packages/twisted/trial/runner.py", line 474, in findByName
    obj = reflect.namedModule(searchName)
  File "/usr/lib/python3.13/site-packages/twisted/python/reflect.py", line 156, in namedModule
    topLevel = __import__(name)
  File "/var/tmp/portage/net-im/synapse-1.115.0-r1/work/synapse-1.115.0/tests/util/test_wheel_timer.py", line 24, in <module>
    from .. import unittest
  File "/var/tmp/portage/net-im/synapse-1.115.0-r1/work/synapse-1.115.0/tests/unittest.py", line 80, in <module>
    from synapse.server import HomeServer
  File "/var/tmp/portage/net-im/synapse-1.115.0-r1/work/synapse-1.115.0-python3_13/install/usr/lib/python3.13/site-packages/synapse/server.py", line 55, in <module>
    from synapse.federation.federation_client import FederationClient
  File "/var/tmp/portage/net-im/synapse-1.115.0-r1/work/synapse-1.115.0-python3_13/install/usr/lib/python3.13/site-packages/synapse/federation/federation_client.py", line 72, in <module>
    from synapse.federation.transport.client import SendJoinResponse
  File "/var/tmp/portage/net-im/synapse-1.115.0-r1/work/synapse-1.115.0-python3_13/install/usr/lib/python3.13/site-packages/synapse/federation/transport/client.py", line 55, in <module>
    from synapse.http.matrixfederationclient import ByteParser, LegacyJsonSendParser
  File "/var/tmp/portage/net-im/synapse-1.115.0-r1/work/synapse-1.115.0-python3_13/install/usr/lib/python3.13/site-packages/synapse/http/matrixfederationclient.py", line 22, in <module>
    import cgi
builtins.ModuleNotFoundError: No module named 'cgi'

tests.util.test_wheel_timer
-------------------------------------------------------------------------------
Ran 370 tests in 3.045s

FAILED (errors=280, successes=90)

Anything else that would be useful to know?

The remaining errors look very similar, therefore I attached just one.

[arkamar]

Fixed in #17741