This is to address #471 that
documented unhelpfull behavour when tracking git sources.

Add warning to git track if track and ref are not present

Closes #471

See merge request !580

This reverts commit 4f168b9b.

The latest version of pytest_pylint works fine with pylint 2, which
means there is no longer a reason to restrict the pylint version.

pylint 2 is required for Python 3.7.

Do not rely on `StopIteration` bubbling up.

https://www.python.org/dev/peps/pep-0479/