MainClass.get_repo() used to default to lazy fetching, which is not what
NamedUser.get_repo() does, so change the default. Fix the tess to pass
lazy=True, so that we don't need to grow 8 ReplayData files with 11
lines of the repository in question.
Fixes#353
The BadAttributes and Enterprise tests made use of try/except to check
details of raised exceptions, so switch to using assertRaises, much like
the github.GithubException tests[1].
1: cf05688359
Steve Kowalik