Use mock compatibility import
Use mock compatibility import

`tests/__init__.py` already has a try/except statement to use mock from
the standard library when possible.  Take advantage of it like other
tests already do.

Signed-off-by: Carl George <de187642e6c75f60d10f29e52cab54cdf676870d@george.computer>

thaJeztah/compose,thaJeztah/compose,dnephin/compose,funkyfuture/docker-compose,vdemeester/compose,shin-/compose,funkyfuture/docker-compose,shin-/compose,vdemeester/compose,dnephin/compose