Remove tox.ini (#20410)

As far as I can tell, no one uses it. @reivilibre also asked this in
[`#synapse-dev:matrix.org`](https://matrix.to/#/!i5D5LLct_DYG-4hQprLzrxdbZ580U9UB6AEgFnk6rZQ/$NrW3QmLEGgcjNqW-SaPZrS-EVwq1-9fO_Ds_1QIZX0E?via=element.io&via=matrix.org&via=starstruck.systems)
and
[`#element-backend-internal:matrix.org`](https://matrix.to/#/!SGNQGPGUwtcPBUotTL:matrix.org/$_rh3S79z4q1Q93SJ3ncQ_ZUzudks4Egan5dwutH2AKg?via=jki.re&via=element.io&via=matrix.org)
on 2026-02-20 with a couple of 🔥 emoji reactions in the public
channel.

As long as I've worked on Synapse, as far as I know, I've never used
this for local dev.

We no longer use this in CI.

Noticed the file again while working on
https://github.com/element-hq/synapse/pull/20359

.gitignore

@@ -55,8 +55,6 @@ tmp/
 /.coverage*
 /.mypy_cache/
 /.ruff_cache/
-/.tox
-/.tox-pg-container
 /build/
 /coverage.*
 /dist/

changelog.d/20410.misc

@@ -0,0 +1 @@
+Remove unused `tox.ini`.

synapse/__init__.py

@@ -95,9 +95,10 @@ import synapse.util  # noqa: E402
 
 __version__ = synapse.util.SYNAPSE_VERSION
 
+# Introduced for usage with SyTest to check that log contexts are correctly handled when
+# running a real homeserver. (our own unit tests apply the same patch unconditionally,
+# in `tests/__init__.py`.)
 if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
-    # We import here so that we don't have to install a bunch of deps when
-    # running the packaging tox test.
     from synapse.util.patch_inline_callbacks import do_patch
 
     do_patch()

tox.ini

@@ -1,104 +0,0 @@
-[tox]
-envlist = py311, py312, py313, py314
-
-# we require tox>=2.3.2 for the fix to https://github.com/tox-dev/tox/issues/208
-minversion = 2.3.2
-
-# the tox-venv plugin makes tox use python's built-in `venv` module rather than
-# the legacy `virtualenv` tool. `virtualenv` embeds its own `pip`, `setuptools`,
-# etc, and ends up being rather unreliable.
-requires = tox-venv
-
-[base]
-deps =
-    python-subunit
-    junitxml
-    coverage
-
-    # this is pinned since it's a bit of an obscure package.
-    coverage-enable-subprocess==1.0
-
-    # cyptography 2.2 requires setuptools >= 18.5
-    #
-    # older versions of virtualenv (?) give us a virtualenv with the same
-    # version of setuptools as is installed on the system python (and tox runs
-    # virtualenv under python3, so we get the version of setuptools that is
-    # installed on that).
-    #
-    # anyway, make sure that we have a recent enough setuptools.
-    setuptools>=18.5
-
-    # we also need a semi-recent version of pip, because old ones fail to
-    # install the "enum34" dependency of cryptography.
-    pip>=10
-
-# default settings for all tox environments
-[testenv]
-deps =
-    {[base]deps}
-extras =
-    # install the optional dependendencies for tox environments without
-    # '-noextras' in their name
-    # (this requires tox 3)
-    !noextras: all
-    test
-
-setenv =
-    # use a postgres db for tox environments with "-postgres" in the name
-    # (see https://tox.readthedocs.io/en/3.20.1/config.html#factors-and-factor-conditional-settings)
-    postgres: SYNAPSE_POSTGRES = 1
-
-    # this is used by .coveragerc to refer to the top of our tree.
-    TOP={toxinidir}
-
-passenv = *
-
-commands =
-    # the "env" invocation enables coverage checking for sub-processes. This is
-    # particularly important when running trial with `-j`, since that will make
-    # it run tests in a subprocess, whose coverage would otherwise not be
-    # tracked.  (It also makes an explicit `coverage run` command redundant.)
-    #
-    # (See https://coverage.readthedocs.io/en/coverage-5.3/subprocess.html.
-    # Note that the `coverage.process_startup()` call is done by
-    # `coverage-enable-subprocess`.)
-    #
-    # we use "env" rather than putting a value in `setenv` so that it is not
-    # inherited by other tox environments.
-    #
-    /usr/bin/env COVERAGE_PROCESS_START={toxinidir}/.coveragerc "{envbindir}/trial" {env:TRIAL_FLAGS:} {posargs:tests} {env:TOXSUFFIX:}
-
-# As of twisted 16.4, trial tries to import the tests as a package (previously
-# it loaded the files explicitly), which means they need to be on the
-# pythonpath. Our sdist doesn't include the 'tests' package, so normally it
-# doesn't work within the tox virtualenv.
-#
-# As a workaround, we tell tox to do install with 'pip -e', which just
-# creates a symlink to the project directory instead of unpacking the sdist.
-#
-# (An alternative to this would be to set PYTHONPATH to include the project
-# directory. Note two problems with this:
-#
-#   - if you set it via `setenv`, then it is also set during the 'install'
-#     phase, which inhibits unpacking the sdist, so the virtualenv isn't
-#     useful for anything else without setting PYTHONPATH similarly.
-#
-#   - `synapse` is also loaded from PYTHONPATH so even if you only set
-#     PYTHONPATH for the test phase, we're still running the tests against
-#     the working copy rather than the contents of the sdist. So frankly
-#     you might as well use -e in the first place.
-#
-# )
-usedevelop=true
-
-
-
-[testenv:benchmark]
-deps =
-    {[base]deps}
-    pyperf
-setenv =
-    SYNAPSE_POSTGRES = 1
-commands =
-    python -m synmark {posargs:}
-