mypy Type error for a class with an imported metaclass

Please provide more information to help us understand the issue:

• Are you reporting a bug, or opening a feature request? bug
• Please insert below the code you are checking with mypy,
  or a mock-up repro if the source is private. We would appreciate
  if you try to simplify your case to a minimal repro.
  Here is an example class I am working with.

@enum.unique
class MyEnumClass(Enum, metaclass=MyEnumMetaClass):
    OUT_OF_STOCK = "Out of Stock"
    LOW_STOCK = "Low Stock"
    IN_STOCK = "In Stock"
    EXCESS = "Excess"

I am making a change where I am importing the MyEnumMetaClass class from a PIP package now, whereas before it was located within the same project as this class.

• What is the actual behavior/output?
  With MyEnumMetaClass imported, whenever I create a MyEnumClass instance, mypy gives me the following error:
  error: The type "Type[MyEnumClass]" is not generic and not indexable
• What is the behavior/output you expect?
  I expect mypy to succeed here, given that the code is the same, it is just imported from a package now.

Start with the supplied minimal enum and metaclass example, checking it once with MyEnumMetaClass defined locally and once when imported from a package. Trace the difference in mypy's handling of the class and confirm that the imported version no longer produces the reported non-generic, non-indexable error.