Python shebang rewrite doesn't support shebang args

[Kyle Fazzari]

A few different plugins (python, catkin) rewrite shebangs like #!/usr/bin/python3 to #!/usr/bin/env python3 . For the most part, this works great. However, some projects (take a look at /usr/bin/lsb_release) actually pass arguments to Python in the shebang, e.g. #!/usr/bin/python3 -Es . /usr/bin/env doesn't support args like this-- it ends up searching for the command 'python3 -Es' which of course doesn't exist.

We need to be smarter about this.

[Kyle Fazzari (kyrofa)]

Proposed fix: https://github.com/snapcore/snapcraft/pull/1719