[Python] Python, subprocess, call(), check_call and returncode to find if a command exists

I've figured out how to use call() to get my python script to run a command:

import subprocess

mycommandline = ['lumberjack', '-sleep all night', '-work all day']
subprocess.call(mycommandline)


This works but there's a problem, what if users don't have lumberjack in their command path? It would work if lumberjack was put in the same directory as the python script, but how does the script know it should look for lumberjack? I figured if there was a command-not-found error then lumberjack wouldn't be in the command path, the script could try to figure out what its directory is and look for lumberjack there and finally warn the user to copy lumberjack into one of those two places if it wasn't found in either one. How do I find out what the error message is? I read that check_call() can return an error message and something about a returncode attribute. I couldn't find examples on how to use check_call() and returncode, what the message would be or how I could tell if the message is command-not-found.

Am I even going about this the right way?

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