allow custom validation of args

lib/config.py

@@ -9,6 +9,15 @@ import sys
 import shutil
 
 
+def module_exists(module_name):
+    try:
+        __import__(module_name)
+    except ImportError:
+        return False
+    else:
+        return True
+
+
 def check_cmake_exists(cmake_command):
     """
     Check whether CMake is installed. If not, print