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: Ifbb4b0bfac3aa146e205726d934d194fea06ff87

celebdor/kuryr-libnetwork,celebdor/kuryr-libnetwork,celebdor/kuryr-libnetwork