Commit ae74f71a1e9d4be043162b19d23f2d44c964c771 removed the pylint unit
test saying that unit tests are not needed to just run flake8 or pylint.
Since pylint is useful, add it back, but this time call it directly and
not embed it into a unit test.
Signed-off-by: Benjamin Drung <benjamin.drung@canonical.com>
Commit ae74f71a1e9d4be043162b19d23f2d44c964c771 removed the flake8
unittest and commit 3428a65b1cd644445f55ad8ae65ece5f73d7acb5 added
running flake8 again, but only for files named `*.py`.
Check also all Python scripts with a Python shebang.
Signed-off-by: Benjamin Drung <benjamin.drung@canonical.com>