bpo-37972: unittest.mock._Call now passes on __getitem__ to the __getattr__ chaining so that call() can be subscriptable

[blhsing]

As reported on StackOverflow:
https://stackoverflow.com/questions/57636747/how-to-perform-assert-has-calls-for-a-getitem-call

The following code:

from unittest.mock import MagicMock, call
mm = MagicMock()
mm().foo()['bar']
print(mm.mock_calls)

would output:

[call(), call().foo(), call().foo().__getitem__('bar')]

But trying to use that list with:

mm.assert_has_calls([call(), call().foo(), call().foo().__getitem__('bar')])

would result in:

TypeError: tuple indices must be integers or slices, not str

This fix now makes unittest.mock._Call.__getattribute__ raise an AttributeError when the given attribute name is '__getitem__' so that __getitem__ can get the same chaining mechanism provided by the __getattr__ method.

https://bugs.python.org/issue37972

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[voidspace]

LGTM. Nice catch and fix.

[miss-islington]

Thanks @blhsing for the PR, and @voidspace for merging it 🌮🎉.. I'm working now to backport this PR to: 3.8.
🐍🍒⛏🤖

[bedevere-bot]

GH-15965 is a backport of this pull request to the 3.8 branch.