Comment 1 for bug 1813860

Please note that upstream CI is likely hiding this issue due to this line in the fix_stuff.sh script:

https://github.com/openstack-dev/devstack/blob/master/tools/fixup_stuff.sh#L244

    if [[ ! -f /etc/ci/mirror_info.sh ]]; then

Clearly downstream CI systems don't have that file, and therefore the code that comes after it:

        pip_install -U --force-reinstall virtualenv

is problematic (since it upgrades to a version of virtualenv that, as Arun says, is incompatible with the version of pip that is locked by devstack).