Convert shebangs to python2
Currently, most (maybe all?) of our shell script shebangs call the 'python' executable, either via /usr/bin/python, or /usr/bin/env python. Many of the platforms we'd like to support either point /usr/bin/python at the python 3 interpreter or do not provide the 'python' interpreter at all. To the best of my knowledge, all of those platforms do provide a 'python2' executable, so for our packages to work on all platforms we want to update our shebangs to be using the '/usr/bin/python2' executable, not '/usr/bin/python' (e.g. /usr/bin/env python2).