[code-quality] Change in unicode escape sequences

[Émanuel Barry]

Hello Code Quality people,
I'm writing to you today about a change that I'm proposing to CPython, which
will warn on invalid Unicode (and bytes) escape sequences, starting 3.6. It
will eventually become an error, although when is yet to be decided. See
http://bugs.python.org/issue27364 for the patch and discussion. First
message sums up pretty well what the end result will be (with maybe a few
minor differences).

As Victor Stinner and Guido both suggested, it would be good to introduce
this in the linters, to help folks who are running e.g. 3.5 (or 2.7 with
plans to migrate). So here I am, asking the maintainers of the linters to
introduce this, hopefully before 3.6.0 hits the shelves in December.

Thanks in advance!
-Emanuel