pylint #111799 W1401 check complains incorrectly about \0, but not \o [validation pending]

The new (in 0.26.0) check for W1401 ("Anomalous backslash in string") has this definition in it, to enumerate the backslash escapes that are meaningful in Python string literals:

ESCAPE_CHARACTERS = 'abfnrtvox\n\r\t\\\'\"'

This is not quite right, though. I think the mistake comes from a confusing table in the Python reference at .

In the escape sequence "\ooo" shown in that table, all of the "o" letters stand for octal digits- there is no "\o" escape in Python. The W1401 check should complain about any "\o" instances in non-raw strings, like it does for \d, etc.

And by the same token, "\0" IS a proper (and common) escape sequence in Python, which W1401 erroneously complains about. (See Footnote 3 after that Python reference escape sequences table; it is supported and ok for there to be only one octal digit in the escape sequence.

done in0.27.0
load left0.000
closed by#720a5ebaba7d string check: don't warn about octal escape sequence, warn about \o (not octal in python). Closes #111799