* --enable-python builds Python programs/modules, fails if no Python found
* --disable-python does not Python programs/modules, regardless of whether
  Python is found or is required for other purposes (e.g. SWIG build)
* passing no option builds Python programs/modules only if Python is found,
  and silently does not Python programs/modules otherwise
Original: 203ff5c4a8e34217eb0c74e569f980845f13ad39