scripts/mod_python.in: replace use of execfile removed in Python 3 (#139)

Python 3 removed the builtin execfile so this replaces it with read,
compile, and exec (see https://stackoverflow.com/questions/436198/).
Because this works in both Python 2 and Python 3, we use this
alternative unconditionally.

Author: carandraug

scripts/mod_python.in

@@ -64,7 +64,9 @@ def cmd_genconfig():
     if len(args) != 1:
         parser.error("Must specify <src>")
 
-    execfile(args[0])
+    src = args[0]
+    with open(src, "rb") as fh:
+        exec(compile(fh.read(), src, "exec"))
 
 def cmd_create():