message: testing: Add both Serial and MPI python tests when possible
  Always add the python bindings Serial tests.  Add the MPI tests when
  ADIOS2 is built with MPI.
diff: #------------------------------------------------------------------------------#
  function(add_python_mpi_test testname)
  - python_add_test(NAME Bindings.Python.${testname} SCRIPT Test${testname}.py
  + python_add_test(NAME Bindings.Python.${testname}.MPI SCRIPT Test${testname}.py
  EXEC_WRAPPER ${MPIEXEC_COMMAND}
  )
  - set_tests_properties(Bindings.Python.${testname} PROPERTIES
  + set_tests_properties(Bindings.Python.${testname}.MPI PROPERTIES
  PROCESSORS "${MPIEXEC_MAX_NUMPROCS}"
  )
  endfunction()
  -python_add_test(NAME Bindings.Python.HighLevelAPI SCRIPT TestHighLevelAPI.py)
  +python_add_test(NAME Bindings.Python.HighLevelAPI.Serial SCRIPT TestHighLevelAPI.py)
  -if(NOT ADIOS2_HAVE_MPI)
  - python_add_test(NAME Bindings.Python.BPWriteReadTypes
  - SCRIPT TestBPWriteReadTypes_nompi.py
  - )
  -endif()
  +python_add_test(NAME Bindings.Python.BPWriteReadTypes.Serial SCRIPT TestBPWriteReadTypes_nompi.py)
  if(ADIOS2_HAVE_MPI)
  add_python_mpi_test(BPWriteReadTypes)
  