Hi @lucyllewy, really appreciate the help and the detail. I will give this a shot this evening.
I am building Python 3.6 and not using the Python plugin as my code has some 3.6 specific syntax and I believe the plugin currently only supports 2.7.x and 3.5.x.
If I want to use 3.6 should I then be installing python to somewhere like $SNAPCRAFT_PART_INSTALL/python. Or maybe it is easier to fork the existing Python plugin and edit it to use 3.6.
Thanks again.