A change for Python 3.8—currently in beta—has produced some
user-visible warnings, but the problem is often in code that a user cannot
(or should not) change: third-party modules. The problem that the warning
is trying to highlight is real, however. The upshot is that the handling of
escape
sequences (or non escape sequences, in truth) in
Python string literals is in a rather messy state at this point.

Source: LWN.net – [$] Escape sequences in Python strings