Use python2 in the shebang

[langston-barrett]

PEP 0394 states that "python should be used in the shebang line only for scripts that are source compatible with both Python 2 and 3."

As such, the first line of terraform.py should read

#!/usr/bin/env python2

[conorsch]

Using env is fine here, you can override python to be whatever version you like via virtualenv or otherwise.