generator: Add support for exercise plugins (#2097)
generator: Add support for exercise plugins (#2097)

* generator: Add support for exercise plugins

* use importlib for importing plugins

* handle plugin SyntaxError

* group SyntaxError with TypeError, UndefinedError

jmluy/xpython,behrtam/xpython,exercism/python,exercism/xpython,behrtam/xpython,exercism/python,exercism/xpython,jmluy/xpython