https://docs.python.org/3/whatsnew/3.6.html#deprecated-python-behavior
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.
The problem appears when you use '-W error':
$ python3 -W error -c 'import re; re.findall("[^a-zA-Z0-9_\-\.]", " *%$")'
File "<string>", line 1
SyntaxError: invalid escape sequence \-
Signed-off-by: Ville Skyttä <ville.skytta@iki.fi>
[ Edited commit message as per suggestion from Petr Lautrbach ]
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>