Determine spec file version silently
    
    Don't log errors when a spec file can't be parsed, there could be any
    number of unparseable versions of the spec file in a repo and we don't
    want to clog up the logs. Just flag it as `None` and let callers work
    around that this is missing.
    
    Signed-off-by: Nils Philippsen <nils@redhat.com>