Get exit code and stderr from subprocess call

Try this version:

import subprocess
try:
    output = subprocess.check_output(
        cmnd, stderr=subprocess.STDOUT, shell=True, timeout=3,
        universal_newlines=True)
except subprocess.CalledProcessError as exc:
    print("Status : FAIL", exc.returncode, exc.output)
else:
    print("Output: \n{}\n".format(output))

This way you will print the output only if the call was successful.
In case of a CalledProcessError you print the return code and the output.