[code-quality] [feature request] Unused variable warning for "except Exception as e"

Hello flake8!

I would have expected pyflakes to emit an unused variables warning for "e" on the following code snippet:

class ModuleError(Exception): pass

try: 1 / 0 except ZeroDivisionError as e: raise ModuleError()

Curious if this check can be added.

Thank you!

-- Shane Creighton-Young shane@goubiq.com