Enable DeprecationWarning in test environments
Enable DeprecationWarning in test environments

Many deprecations are triggered early (on imports, for example)
before the warnings are enabled by the WarningsFixture in the
base test class.

To make sure all DeprecationWarning messages are emitted we enable
them via the PYTHONWARNINGS environment variable.

Change-Id: I1a8c6e305ccb9244eb7c690a93921d0982b3ecbe

openstack/neutron-vpnaas,openstack/neutron-vpnaas