lower-constraints are not used in gate job

Change abandoned by sean mooney (<email address hidden>) on branch: master
Review: https://review.openstack.org/645392
Reason: we are going with https://review.openstack.org/#/c/622972/ instead

Reviewed: https://review.openstack.org/622972
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=e5269f2fbb773953266fccbfd9df3f75e351eeb9
Submitter: Zuul
Branch: master

commit e5269f2fbb773953266fccbfd9df3f75e351eeb9
Author: Chris Dent <email address hidden>
Date: Wed Dec 5 14:01:04 2018 +0000

    Correct lower-constraints.txt and the related tox job

    In the review of a similar change in placement [1], it was realized that
    the nova lower-constraints tox job probably had the same problems.
    Testing revealed this to be the case. This change fixes the job and
    updates the related requirements problems accordingly.

    The are two main factors at play here:

    * The default install_command in tox.ini uses the upper_contraints.txt
      file. When there is more than one constraints.txt they are merged and
      the higher constraints win. Using upper and lower at the same time
      violates the point of lower (which is to indicate the bare minimum
      we are capable of using).

    * When usedevelop is true in tox, the command that is run to install the
      current projects code is something like 'python setup.py develop',
      which installs a project's requirements _after_ the install_command has
      run, clobbering the constrained installs. When using pbr,
      'python setup.py install' (used when usedevelop is False) does not do
      this.

    Fixing those then makes it possible to use the test to fix the
    lower-constraints.txt and *requirements.txt files, changes include:

    * Defining 'usedevelop = False' in the 'lower-constraints' target and
      removing the otherwise superfluous 'skipsdist' global setting to
      ensure requirements aren't clobbered.

    * Removing packages which show up in lower-constraints.txt but not in
      the created virtualenv. Note that the job only runs unit tests, so
      this may be incomplete. In the placement version of this both unit and
      functional are run. We may want to consider that here.

    * Updating cryptography. This version is needed with more recent
      pyopenssl.

    * Updated keystonemiddleware. This is needed for some tests which
      confirm passing configuration to the middleware.

    * Update psycopg2 to a version that can talk with postgresql 10.

    * Add PyJWT, used by zVMCloudConnector

    * Update zVMCloudConnector to a version that works with Python 3.5 and
      beyond.

    * Update olso.messaging to versions that work with the tests, under
      Python 3.

    * Adding missing transitive packages.

    * Adjusting alpha-ordering to map to how pip freeze does it.

    * setuptools is removed from requirements.txt because the created
      virtualenv doesn't contain it

    NOTE: The lower-constraints.txt file makes no commitment to expressing
    minimum requirements for anything other than the current basepython.
    So the fact that a different set of lower-constraints would be present
    if we were using python2 is not relevant. See discussion at [1].
    However, since requirements.txt _is_ used for python2, the
    requirements-check gat...

This issue was fixed in the openstack/nova 20.0.0.0rc1 release candidate.