Fix some oddities in the DBResolver implementation of
get_compatible_base_module_modulemds() and make the MBSResolver version -
which was previously just buggy - match that. (Tests for the MBSResolver
version are added in a subsequent commit.)
* If an empty virtual_streams argument was passed in, *all* streams
were considered compatible. Throw an exception in this case - it
should be considered an error.
* If stream_version_lte=True, but the stream from the base module
wasn't in the form FOOx.y.z, then throw an exception. This was
previously treated like stream_version_lte=False, which is just
a recipe for confusion and mistakes.
test_get_reusable_module_use_latest_build() is rewritten to
comprehensively test all possibilities, including the case that changed
above.
test_add_default_modules_compatible_platforms() is changed to run
under allow_only_compatible_base_modules=False, since it expected
Fedora-style virtual streams (versions not in FOOx.y.z form, all
share the same stream), which doesn't make sense with
allow_only_compatible_base_modules=True.
No implementations of MBS are using Greenwave, and there are no current plans
to do so. Koji Resolver will be sufficient for any usecase dependent on gating.
This also includes `from __future__ import absolute_import`
in every file so that the imports are consistent in Python 2 and 3.
The Python 2 tests fail without this.
