Slight update for Python scripts

tools/make-firefox-meta.py

@@ -3,10 +3,11 @@
 import os
 import json
 import sys
+from io import open
 from shutil import rmtree
 from collections import OrderedDict
 
-if not sys.argv[1]:
+if len(sys.argv) == 1 or not sys.argv[1]:
     raise SystemExit('Build dir missing.')