Description

Resolves #2143

In Python 3.11 mocking of attributes through unittest.mock.patch will fail with an AttributeError. To avoid this, use unittest.mock.patch.object to mock the _setup attribute of a pyhf.tensorlib object.

c.f. https://docs.python.org/3.11/library/unittest.mock.html#the-mock-class footnote:

The only exceptions are magic methods and attributes (those that have leading and trailing double underscores). Mock doesn’t create these but instead raises an AttributeError. This is because the interpreter will often implicitly request these methods, and gets very confused to get a new Mock object when it expects a magic method

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* In Python 3.11 mocking of attributes through unittest.mock.patch will
  fail with an AttributeError. To avoid this, use unittest.mock.patch.object
  to mock the "_setup" attribute of a pyhf.tensorlib object.
   - c.f. https://docs.python.org/3.11/library/unittest.mock.html#the-mock-class
     footnote:

     > The only exceptions are magic methods and attributes (those that have
     > leading and trailing double underscores). Mock doesn’t create these but
     > instead raises an AttributeError. This is because the interpreter will
     > often implicitly request these methods, and gets very confused to get a
     > new Mock object when it expects a magic method.