Update pylint to 2.3.1
Depends on D6404
- Added a new command line option `list-groups for listing all the check groups pylint` knows about.
- Allow `BaseException for emitting broad-except, just like Exception`.
- Fixed a crash that occurred for `bad-str-strip-call when strip() received None`
- Don't emit `*-not-iterating checks for builtins consumed by itertools`
- Fix a crash caused by iterating over `Uninferable` in a string formatting check.