debuginfo-install: doesn't install latest pkgs (RhBug: 1096507)

This is caused because I've installed 'p' (current provider), but we
need to install 'pkg', which correctly throw installed and available
packages.

Reference: https://bugzilla.redhat.com/show_bug.cgi?id=1096507
py3: absolute imports and unicode literals everywhere.

Avoids surprises later.
copr: remove repofile if failed to enable repo

If we trying to enable repo - it trying to download and creating
repofile, but when it's failed (generally Copr repo doesn't exist) -
it's not deleting this repofile.