[tahoe-lafs-trac-stream] [Tahoe-LAFS] #2876: tox won't run on ubuntu xenial: python3

[Tahoe-LAFS]

#2876: tox won't run on ubuntu xenial: python3
-----------------------+------------------------
 Reporter:  warner     |          Owner:  daira
     Type:  defect     |         Status:  new
 Priority:  major      |      Milestone:  1.13.0
Component:  packaging  |        Version:  1.12.1
 Keywords:             |  Launchpad Bug:
-----------------------+------------------------
 We recently landed a change to our `setup.py`, to bail with a clear error
 message if you try to run it under python3 (since tahoe only supports
 python2). Unfortunately, the `tox` provided in Ubuntu-16.04 "xenial" (the
 most recent LTS release) is a python3 executable, and when it runs
 `setup.py` to build a .zip package, it fails:

 {{{
 $ tox -e py27
 GLOB sdist-make: /home/bb-tahoe/bb-
 tahoe/Ubuntu_xenial_16_04/build/setup.py
 ERROR: invocation failed (exit code 1), logfile: /home/bb-tahoe/bb-
 tahoe/Ubuntu_xenial_16_04/build/.tox/log/tox-0.log
 ERROR: actionid: tox
 msg: packaging
 cmdargs: ['/usr/bin/python3', local('/home/bb-tahoe/bb-
 tahoe/Ubuntu_xenial_16_04/build/setup.py'), 'sdist', '--formats=zip',
 '--dist-dir', local('/home/bb-tahoe/bb-
 tahoe/Ubuntu_xenial_16_04/build/.tox/dist')]
 env: None

 Traceback (most recent call last):
   File "setup.py", line 32, in <module>
     raise RuntimeError("Python version 2 is required")
 RuntimeError: Python version 2 is required

 ERROR: FAIL could not package project - v =
 InvocationError('/usr/bin/python3 /home/bb-tahoe/bb-
 tahoe/Ubuntu_xenial_16_04/build/setup.py sdist --formats=zip --dist-dir
 /home/bb-tahoe/bb-tahoe/Ubuntu_xenial_16_04/build/.tox/dist (see /home/bb-
 tahoe/bb-tahoe/Ubuntu_xenial_16_04/build/.tox/log/tox-0.log)', 1)
 }}}

 As a result, our xenial buildbot is failing, and folks using xenial can't
 test tahoe.

 I'm a bit surprised that tox is using it's native python3 to build a
 package, even though the `-e py27` should cause it to use python2 to
 actually run the tests. Is there some way to tell tox which python to use
 for packaging purposes?

--
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2876>
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