Python 2.x and 3.x compatible changes

Changes:
    - Update imports and syntax.

Resolves  openbmc/openbmc-test-automation#1426

Change-Id: I4cf400429c5f863ed8f30d24fa871b1c564d9f2a
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/lib/gen_arg.py b/lib/gen_arg.py
index 313a486..7c82ece 100755
--- a/lib/gen_arg.py
+++ b/lib/gen_arg.py
@@ -6,7 +6,10 @@
 """
 
 import sys
-import __builtin__
+try:
+    import __builtin__
+except ImportError:
+    import builtins as __builtin__
 import atexit
 import signal
 import argparse