flake8: Enable W605 check

Merged Dmitry Volodin requested to merge noc-flake-W605 into master
W605 invalid escape sequence 'x'
   As of Python 3.6, a backslash-character pair that is
   not a valid escape sequence now generates a DeprecationWarning.
   Although this will eventually become a SyntaxError,
   that will not be for several Python releases.
   Not an actual error for Python2 and breaks already passed tests.
   Postponed for a while

Предварительная работа уже проведена, проверка становится обязательной.

Edited by Dmitry Volodin

Merge request reports