Comment 2 for bug 1824189

Reviewed: https://review.openstack.org/651598
Committed: https://git.openstack.org/cgit/openstack/ansible-role-python_venv_build/commit/?id=b2abfe4bad7e7b440e79b048461cfbfda2b06757
Submitter: Zuul
Branch: master

commit b2abfe4bad7e7b440e79b048461cfbfda2b06757
Author: Mohammed Naser <email address hidden>
Date: Wed Apr 10 12:18:45 2019 -0400

    Delete constraints and requirements files on build fail

    If the installation of Python packages fails for any reason, the
    constraint and requirements file is already written and therefore
    unless you delete the virtualenv, it would not rebuild things
    again.

    This patch will handle failure and delete those files, then provide
    a warning for the user upon failing to inspect the needed file.

    Closes-Bug: #1824189

    Change-Id: I67db44ce10250908f23c26c90d271a780a875eb6