stack.sh fails on installing setuptools

[Radosław Piliszek]

All DevStack CI jobs are broken due to setuptools not available for Python 2.

stack.sh uses the unversioned python, which is usually Python 2 still (including Ubuntu Bionic), and fails with:
UnsupportedPythonVersion: Package 'setuptools' requires a different Python: 2.7.17 not in '>=3.5'

[Radosław Piliszek (yoctozepto)]

Notice USE_PYTHON3=True does not help as stack.sh is hardcoded to versionless Python.

[Radosław Piliszek (yoctozepto)]

https://setuptools.readthedocs.io/en/latest/history.html#v45-0-0
#1458: Drop support for Python 2. Setuptools now requires Python 3.5 or later. Install setuptools using pip >=9 or pin to Setuptools <45 to maintain 2.7 support.

PS:
#1959: Fix for Python 4: replace unsafe six.PY3 with six.PY2
here we go again :-)

[Radosław Piliszek (yoctozepto)]

So this is due to using virtualenv which calls old pip to install latest pip and friends.
The easiest fix for gate is to update system pip before running virtualenv.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/702140

[Radosław Piliszek (yoctozepto)]

going py3 also fixes this issue of course: https://review.opendev.org/702131

[Radosław Piliszek (yoctozepto)]

Unfortunately, it seems pip was already 9 but virtualenv does not use the modern version resolver and keeps trying latest.

[Radosław Piliszek (yoctozepto)]

The issue has been reported independently to virtualenv not so long ago: https://github.com/pypa/virtualenv/issues/1493

[OpenStack Infra (hudson-openstack)]

Change abandoned by Radosław Piliszek (<email address hidden>) on branch: master
Review: https://review.opendev.org/702140
Reason: not the way forward (I don't like the pin either heh)

[Radosław Piliszek (yoctozepto)]

fixed by removing the offending wheel