iotests: Run pylint and mypy in a testcase

iotests: Run pylint and mypy in a testcase

We made sure that iotests.py passes pylint. It would be a shame if we
allowed new patches in that break this again, so let's just add a
meta-test case that runs pylint on it.

While we don't pass mypy --strict yet, we can already run it with a few
options that would be part of --strict to make sure that we won't
regress on these aspects at least until we can enable the full thing.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200511163529.349329-3-kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>