CMake: fix broken logic around Python

CMakeLists.txt

@@ -180,10 +180,12 @@ if ( PYTHONLIBS_FOUND )
     )
 endif()
 
-if( PYTHONLIBS_NOTFOUND OR NOT CALAMARES_BOOST_PYTHON3_FOUND )
+if( NOT PYTHONLIBS_FOUND OR NOT CALAMARES_BOOST_PYTHON3_FOUND )
+    message(STATUS "Disabling Boost::Python modules")
     set( WITH_PYTHON OFF )
 endif()
-if( PYTHONLIBS_NOTFOUND OR NOT PYTHONQT_FOUND )
+if( NOT PYTHONLIBS_FOUND OR NOT PYTHONQT_FOUND )
+    message(STATUS "Disabling PythonQt modules")
     set( WITH_PYTHONQT OFF )
 endif()