Update make_deb.py to work for Python2 or 3

[aiuto]

Generally being more careful about unicode handling.
Some very weird magic with pre-processing argv to undo undesired interpreter behavior.

This leaves the code in a state where someone could use either interpreter.
Next step it to figure out how to select the python version to match whatever toolchain we have.

[aiuto]

Mostly fixes #35
@qzmfranklin, @jwnimmer-tri Do you want to patch this in, change the target to PY3 and see if it works for you?

[brandjon]

Next step it to figure out how to select the python version to match whatever toolchain we have.

bazelbuild/bazel#8713. I think the easiest thing is to make it python_version = "PY3" since that's preferred, but keep it compatible with PY2 (enforced via a python_version = "PY2" py_test). In the host config you don't control its real Python version anyway.

If a user doesn't have Python 3 installed but wants to run targets marked PY3 that are in reality compatible with both Python 2 and 3, they should use the non-strict toolchain (implemented in bazelbuild/bazel#8547).

[brandjon]

Not super familiar with this code but looks plausible.

[aiuto]

Also changed the default version to py3 and added a py2 test.

[aiuto]

Mostly fixes #35
@qzmfranklin, @jwnimmer-tri Do you want to patch this in, change the target to PY3 and see if it works for you?

I added changed to PY3 as the default and added a py2 test, so this is less important. I think I will merge and we'll see how that goes.

[jwnimmer-tri]

Thanks for your work on this! Apologies for the slow reply, I have been on vacation.

I tested the latest master here 96e34ab against my tree, and I can confirm that the decode()-related problems I saw in bazelbuild/bazel/issues/7370 are resolved.