If you build pipe_tasks against
DM-11514, testFakes.py fails.
The problem is in testFakeMaskAdded(), which tries to verify the process of adding a mask to afw.image.Mask.MaskPlaneDict by instantiating a MaskPlaneDict, verifying that the mask key FAKE is not in the dict, and then instantiating the test class TrialFakeSourceTask(), which does have a FAKE mask, and verifying that FAKE is in the MaskPlaneDict associated with the new instance.
The problem is that testFakeProcessing.py already instantiated a task with the same config as TrialFakeSourceTask. Thus, when testFakes.py first calls lsst.afw.image.Mask().getMaskPlaneDict(), FAKE is already in the MaskPlaneDict, and the assertNotIn meant to verify that FAKE doesn't exist fails.
I am not sure whether or not it is a bug that instantiating FakeSourceTestTask in testFakeProcessing.py causes the FAKE key to be added to lsst.afw.image.Mask().getMaskPlaneDict() or not.