sqlalchemy-migrate fails to install with latest setuptools because Tempita requires 2to3

[Victor Stinner]

While running our tool to test the buildbot configuration, I got an error when pip tried to install Tempita:

  Using cached Tempita-0.5.1.tar.gz (12 kB)
    ERROR: Command errored out with exit status 1:
     command: /home/vstinner/python/buildmaster-config/env2/bin/python -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-iqp4oboj/tempita_9c6d1d583b824ff7b2b23b57e8e32c40/setup.py'"'"'; __file__='"'"'/tmp/pip-install-iqp4oboj/tempita_9c6d1d583b824ff7b2b23b57e8e32c40/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-3ozhl4cx
         cwd: /tmp/pip-install-iqp4oboj/tempita_9c6d1d583b824ff7b2b23b57e8e32c40/
    Complete output (1 lines):
    error in Tempita setup command: use_2to3 is invalid.
    ----------------------------------------

buildbot-www depends on sqlalchemy-migrate which depends on Tempita: requirements.txt contains "Tempita>=0.4".
https://opendev.org/x/sqlalchemy-migrate/src/branch/master/requirements.txt

setuptools 58.0 contains a breaking change:

"#2086: Removed support for 2to3 during builds. Projects should port to a unified codebase or pin to an older version of Setuptools using PEP 518 build-requires."
https://setuptools.readthedocs.io/en/latest/history.html#v58-0-0

Tempita latest release was 8 years ago. Could sqlalchemy-migrate not depend on it? Or can someone try to update Tempita to avoid 2to3?

[Victor Stinner (vstinner)]

Workaround: block setuptools 58 and newer.

Example: https://github.com/python/buildmaster-config/commit/73a70b5e0a94d4c94e518c5d1f9b02f691b23e3d

[Victor Stinner (vstinner)]

Well, buildbot fixed the issue by... replacing sqlachemy-migrate with alembic.

https://github.com/buildbot/buildbot/pull/6224