Unix/Linux systems have a simple (but useful) tool named which, whose main purpose is to indicate where in the filesystem a particular executable is installed. This functionality was added in Python 3.3, and though simple, I was looking forward to its availability in Debian, just so I could replace wajig's own equivalent functionality, which only checked for file presence, and was hard-coded and therefore inflexible. shutil.which(), OTOH, looks for the given executable name in user's PATH and is more thorough, since it also checks if the executable name points to something that is actually executable. So, making use of this new function resulted in code that is both more robust and cleaner.
As a sidenote, this functionality was first proposed in 2001!