Inspired from the tox_install script in the python-openstackclient, this
commit brings in the following improvements to glance_store's
* Do not leave temporary directory around, instead delete temporary
directory directly after usage (change
* Do not set ZUUL_BRANCH explicitely and remove unused if condition
This will force pip install to use the upper-constraints.txt specified
version of pip modules. When you don't do this, you are out on the
bleeding edge and become unstable everytime some python library in the
wide world changes in a way that you don't expect.
There are a few 'post' jobs as Andreas has mentioned on this review,
that have the install_command overridden (until that will be supported
in upstream infra).
This change has been inspired by
Ie1133e4c020106e8098685ba9125f84b356d8e0c , notes from jaegerandi in the
openstack/glance's tox.ini file and Ihar's python-neutronclient's fix