Custom Errors

[s2t2]

Add to errors.md:

class MyCustomError(Exception):
   pass

raise MyCustomError("My custom message")

h/t:

• https://stackoverflow.com/questions/1319615/proper-way-to-declare-custom-exceptions-in-modern-python
• https://www.programiz.com/python-programming/user-defined-exception
• https://docs.python.org/3.7/library/exceptions.html