Show HN: Use Python docstrings as exception messages

The following exception

  @dataclass
  class PodBayDoorsStillClosed(DocumentedError):
      """
      I’m sorry, {self.user_name}.

      I’m afraid I can’t do that.
      """

      user_name: str

when raised as

  raise PodBayDoorsStillClosed('Dave')

will print

  PodBayDoorsStillClosed: I’m sorry, Dave.

  I’m afraid I can’t do that.

Reduce the boilerplate, use more exception classes to better express the business logic, or invent your own use cases :) Can be tried out as:

  pip install documented

which works for Python ⩾ 3.8.1.