nova-powervm tox pep8 fails for py3

[Matthew Edmonds]

I'm seeing the following error when I run `tox -re epep8` for nova-powervm (master) on a new Ubuntu 16.04.2 system:

Traceback (most recent call last):
  File ".tox/pep8/bin/flake8", line 11, in <module>
    sys.exit(main())
  File "/home/edmondsw/openstack/nova-powervm/.tox/pep8/lib/python3.5/site-packages/flake8/main.py", line 28, in main
    flake8_style = get_style_guide(parse_argv=True)
  File "/home/edmondsw/openstack/nova-powervm/.tox/pep8/lib/python3.5/site-packages/flake8/engine.py", line 234, in get_style_guide
    styleguide = StyleGuide(**kwargs)
  File "/home/edmondsw/openstack/nova-powervm/.tox/pep8/lib/python3.5/site-packages/flake8/engine.py", line 154, in __init__
    self._styleguide = kwargs.pop('styleguide', NoQAStyleGuide(**kwargs))
  File "/home/edmondsw/openstack/nova-powervm/.tox/pep8/lib/python3.5/site-packages/pep8.py", line 1651, in __init__
    options.logical_checks = self.get_checks('logical_line')
  File "/home/edmondsw/openstack/nova-powervm/.tox/pep8/lib/python3.5/site-packages/pep8.py", line 1747, in get_checks
    return sorted(checks)
TypeError: unorderable types: function() < function()

This appears to be specific to py3. If I change the tox.ini to make pep8 use py2.7, this error goes away.

Interestingly, nova is already forcing py2.7 for pep8 because py3 wasn't working for them [1]. The trace for the nova bug [2] looks different, but still...

[1] https://github.com/openstack/nova/commit/05583d14966a366f0d37753b81c8f72c87126348
[2] https://bugs.launchpad.net/designate/+bug/1456955

[Matthew Edmonds (edmondsw)]

I should mention that realpath `which python` returns /usr/bin/python2.7, so I have no idea why tox was using python3.5

[Matthew Edmonds (edmondsw)]

flake8 version 2.5.5, pep8 version 1.7.0.

I also tried downgrading pep8 to 1.5.7 and the error persisted as long as tox was using py3.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/490014

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/490014
Committed: https://git.openstack.org/cgit/openstack/nova-powervm/commit/?id=b4eed72d1cd91fe0a246641f0ffb7701a85241b6
Submitter: Jenkins
Branch: master

commit b4eed72d1cd91fe0a246641f0ffb7701a85241b6
Author: Matthew Edmonds <email address hidden>
Date: Wed Aug 2 08:54:49 2017 -0400

    force python2.7 for tox pep8

    tox -re pep8 isn't working for systems that use python 3. Force tox
    to use python2.7 for pep8.

    Change-Id: I61468c3e3ab673dc84248dc72d1085c83ee57bc0
    Closes-Bug: #1708163