Setting both USE_SYSTEM_python2 and USE_SYSTEM_python3 disables python
if (python_enabled AND
((USE_SYSTEM_python2 AND NOT python2_FIND_LIBRARIES) OR
(USE_SYSTEM_python3 AND NOT python3_FIND_LIBRARIES)))
set(PARAVIEW_USE_PYTHON OFF)
Since the various 'python*_FIND_LIBRARIES' values default to undefined (False), this whole thing evaluates to True if both the USE_SYSTEM_python* options are enabled.
This usually means 'surprise!' no pvpython or pvbatch were built and the ctest cpack step fails.
Edited by Paul Ferrell