Interestingly only shows in particular python versions
on travis.
Maybe some caching effect?

Locally it is reproducible easily, with the latest flake8

When the code is run without setting up loggers, the loggers have no
handlers for the emitted messages. The logging module displays:
`No handlers could be found for logger "git.cmd"` on the
console. By adding a NullHandler (a no-op) the message disappears,
and doesn't affect logging when other handlers are configured.

Previously we could try to remove the branch we are on.
Of course, we have a test-case elaborate enough to verify we don't
destroy changes in submodules accidentally. Therefore I am confident
that this implementation is correct.

Fixes #49