Use except x as y instead of except x, y

According to https://docs.python.org/3/howto/pyporting.html the
syntax changed in Python 3.x. The new syntax is usable with
Python >= 2.6 and should be preferred to be compatible with Python3.

Change-Id: Icd4574c55c9460bd29a8adc84d527a4459eb3cf6