Improvements on the PEP8 checks
The output of the PEP8 checks duplicate the error messages and do not show the line with the error (as described by [changeset:d14c2803eca669022a64a5caf16699ce77e2fb70/stem d14c2803eca669022a64a5caf16699ce77e2fb70]). Patch 0001 fixes this bug.
While fixing this bug, i checked the custom checks done in
stylistic_issues and found two checks that are already done by the pep8 library. Patch 0002 and 0003 remove the custom checks in favor of the pep8 library.