As of Python 3.3, the 3rd-party `mock` package has been subsumed into the
standard `unittest.mock` package. Refactoring tests to use the latter will
allow us to drop `mock` as a dependency, which is currently coming in
transitively through requirements/edx/paver.in.
We don't actually drop the `mock` dependency in this PR. That will happen
naturally in:
* https://github.com/openedx/edx-platform/pull/34830
As part of dissolving our sub-projects in edx-platform, we are moving this package under the xmodule directory.
We have fixed all the occurences of import of this package and also fixed all documents related references.
This might break your platform if you have any reference of `import capa` or `from capa import` in your codebase or in any Xblock.
Ref: https://openedx.atlassian.net/browse/BOM-2582
