Do not suggest NotImplemented for raise and except

[cdce8p]

Environment data

• Language Server version: 2020.10.3
• OS and version: macOS
• Python version: 3.9

Expected/Suggested behaviour

Do not suggest NotImplemented for raise and except. It should always be NotImplementedError.
Unfortunately this is quite a common issue, especially with beginners.

Code Snippet / Additional information

[cdce8p]

To expand on that idea:

• Limit suggestions to classes and instances that inherit from BaseException
• Expand Pylance check Type[MyClass] is not a valid exception class to cover raise and variables.

class MyClass:
  pass

try:
  raise MyClass  # No error here
except MyClass:  # Type[MyClass] is not a valid exception class
  pass


my_var = None
raise my_var     # No error

[jakebailey]

We'd need to decide if it's worth only showing things that are exceptions after raise/except; one gotcha is that it's totally legal to write something like some.module.MyException or Some.NestedException, and filtering the list early would mean you wouldn't get any completions until you eventually find some object that contains an exception.