image saver shebang can use python 2

[KaushikMalapati]

image_saver requires python 3 because it uses nonlocal, we should try changing it to #!/usr/bin/python3 or #!/usr/bin/env python3

[ZLLentz]

Even with the built-in python3 binaries this will still break, right? I suppose we'll get a more sensible error at least.
It might be possible to use a full path to a pcds_conda python3 binary, or if not another approach would be to set up the correct environment using a wrapper bash script.

[KaushikMalapati]

A wrapper bash script is probably the way to go