BashOperator - resolve bash by absolute path

[MatrixManAtYrService]

Fixes #25330

Necessary because maybe the user sets env but doesn't set PATH. Now PATH is empty and the subprocess can't find bash. I'm a little confused why this is not a more common failure mode, does subprocess have a list of default locations to look or something?

Existing tests of BashOperator should be sufficient.

[uranusjr]

I'm a little confused why this is not a more common failure mode, does subprocess have a list of default locations to look or something?

Yes, kind of. When you supply a “bare“ command (instead of a path), subprocess relies on the OS to look up the actual executable. This is the same as looking up in PATH most of the time, but also depends on a bunch of other run-time configurations set in the OS. So the general suggestion is to always pass in a pre-resolved path instead of a bare command, since it is the behaviour most people expect in most situations, unless you are actively trying to replicate the OS behaviour down to implementation details.

This is also mentioned in the subprocess documentation: https://docs.python.org/3.10/library/subprocess.html#subprocess.Popen

[potiuk]

This is also mentioned in the subprocess documentation: https://docs.python.org/3.10/library/subprocess.html#subprocess.Popen

TIL. Thanks @MatrixManAtYrService and @uranusjr for nice discussion on it and links :)