Special conversions of xrange() #10556

Documenting these requests so they do not get lost...

#10525 attempted to convert all calls to six.moves.xrange() into calls to range() as part of the removal of Python 2 support. There were several suggestions to make alternative conversions:

• These functions should just be deleted as they have been deprecated since 2.1: one and two
• Probably better written using np.stack() or a variant of it: one and two
• Probably should be itertools.count(): one

After these changes are made, the lines containing from six.moves import xrange should also be removed.