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: I28c95750cfd1a52eaa282db983ca9f4d5f7ea43f

stackforge/networking-arista,openstack/networking-arista,openstack/networking-arista