First noted in change id by fumihiko and kyle:
I079e18b58b214bf8362945c253d6d894ca8b1a6b
Neutron and few others seem to use an extra "python" along
with run_process which is quite unnecessary and complicates
adding python3 support in devstack. So let's clean this up.
Change-Id: I2d478f2b04c04d05c18420563e2ad77eba73be3f