>>> isinstance(2, 1)
Traceback (most recent call last):
  ...
TypeError: isinstance() arg 2 must be a type, a tuple of types or a union
>>> issubclass(int, 1)
Traceback (most recent call last):
  ..
TypeError: issubclass() arg 2 must be a class, a tuple of classes, or a union.

1) It should be "an union", not "a union".
2) The punctuation marks aren't the same -- there's a comma before "or" in issubclass, but not isinstance(). And issubclass()'s ends with a period, which isn't the same with other builtins' messages.