functional: always enable all python warnings

functional: always enable all python warnings

Of most importance is that this gives us a heads-up if anything
we rely on has been deprecated. The default python behaviour
only emits a warning if triggered from __main__ which is very
limited.

Setting the env variable further ensures that any python child
processes will also display warnings.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20250715143023.1851000-11-berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>