Implement flake8-raise

[ngnpope]

GitHub, PyPI.

• R100: raise in except handler without from
  • Already implemented via B904 from flake8-bugbear
  • Already implemented via TRY200 from tryceratops
    • This is buggy and only triggers with raise Exception() and not raise Exception (no parentheses)
  • Maybe implementation for one of these should be scrapped with the error code aliased to the other? 🤔
• R101: use bare raise in except handler
  • Already implemented via TRY201 from tryceratops
• R102: unnecessary parentheses on raised exception

So this plugin is mostly implemented. R102 looks like it should be a relatively easy rule to define.

[charliermarsh]

Just confirming that in addition to adding R102, we should:

1. Remove B904, and mark it as an alias of TRY200.
2. Fix TRY200 to flag raise Exception (without parentheses).

[ngnpope]

Yeah, sounds good. I guess it makes sense to keep TRY200 over B904 as tryceratops is exception-focused and flake8-bugbear is a random collection of stuff.