Understand virtual base classes

[pylint-bot]

Originally reported by: Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore?)

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#!python

import abc

class MyInt(metaclass=abc.ABCMeta):
   pass

print(MyInt.register(int))
print(issubclass(int, MyInt)) # should return True

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• Bitbucket: https://bitbucket.org/logilab/astroid/issue/193