Remove magic hack

It should be assumed that on modern development environments, python
is accessible to /usr/bin/env

Change the shebang as necessary and remove the magic hack.

This also means losing the -E option on the call to python, so that
PYTHONPATH and PYTHONHOME will be respected and local configuration
problems in those vars would be noticed

Change-Id: I6f0708ca7693f05a4c3621c338f03619563ba630