Fix in `find_python_module` cmake function `REQUIRED` flag; adapt function so...

Fix in `find_python_module` cmake function `REQUIRED` flag; adapt function so that it prints cause of error

cmake/modules/RootNewMacros.cmake

@@ -955,24 +955,28 @@ endfunction()
 # find_python_module(module [REQUIRED])
 #----------------------------------------------------------------------------
 function(find_python_module module)
-  string(TOUPPER ${module} module_upper)
-  if(NOT PY_${module_upper})
-    if(ARGC GREATER 1 AND ARGV1 STREQUAL "REQUIRED")
-      set(${module}_FIND_REQUIRED TRUE)
-    endif()
-    # A module's location is usually a directory, but for binary modules
-    # it's a .so file.
-    execute_process(COMMAND "${PYTHON_EXECUTABLE}" "-c"
-      "import re, ${module}; print(re.compile('/__init__.py.*').sub('',${module}.__file__))"
-      RESULT_VARIABLE _${module}_status
-      OUTPUT_VARIABLE _${module}_location
-      ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
-    if(NOT _${module}_status)
-      set(PY_${module_upper} ${_${module}_location} CACHE STRING  "Location of Python module ${module}")
-    endif()
-  endif()
-  find_package_handle_standard_args(PY_${module} DEFAULT_MSG PY_${module_upper})
-  set(PY_${module_upper}_FOUND ${PY_${module_upper}_FOUND} PARENT_SCOPE) 
+   string(TOUPPER ${module} module_upper)
+   if(NOT PY_${module_upper})
+      if(ARGC GREATER 1 AND ARGV1 STREQUAL "REQUIRED")
+         set(py_${module}_FIND_REQUIRED TRUE)
+      endif()
+      # A module's location is usually a directory, but for binary modules
+      # it's a .so file.
+      execute_process(COMMAND "${PYTHON_EXECUTABLE}" "-c"
+         "import re, ${module}; print(re.compile('/__init__.py.*').sub('',${module}.__file__))"
+         RESULT_VARIABLE _${module}_status
+         OUTPUT_VARIABLE _${module}_location
+         ERROR_VARIABLE _${module}_error
+         OUTPUT_STRIP_TRAILING_WHITESPACE
+         ERROR_STRIP_TRAILING_WHITESPACE)
+      if(NOT _${module}_status)
+         set(PY_${module_upper} ${_${module}_location} CACHE STRING "Location of Python module ${module}")
+      else(NOT _${module}_status)
+         message(STATUS "Failed to find Python module ${module}: ${_${module}_error}")
+      endif()
+   endif()
+   find_package_handle_standard_args(py_${module} DEFAULT_MSG PY_${module_upper})
+   set(PY_${module_upper}_FOUND ${PY_${module_upper}_FOUND} PARENT_SCOPE)
 endfunction()