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.