`sudo` is not using the right binary, even when $PATH is correctly passed

Question

I am trying to run a Pipenv python instance as root. When not run as root:

(myenv) $ python script.py

the Pipenv python is correctly used. However, when run as root with sudo:

(myenv) $ sudo python script.py

the system default python at /usr/bin/python is used instead. After some searching, I found the -E option for sudo. However, with

(myenv) $ sudo -E python script.py

it still uses /usr/bin/python, even though sudo -E echo $PATH gives the same as echo $PATH, so the -E option works fine; however, sudo -E which python continues to give /usr/bin/python! It is not a permissions or access problem because the full path to the Pipenv python works fine. Why is the wrong binary being used even though $PATH is set correctly?

Answer 1

Ok, here's the problem. When I was troubleshooting, I wanted to find the value of $PATH inside sudo. However, with sudo -E echo $PATH, my user (non-sudo) shell was expanding it automatically, so sudo just saw

echo /home/user/.local/share/virtualenvs/environment-_Sko9eTd/bin:/usr/bin/:......

Trying sudo -E env tells us the real story:

LANGUAGE=en_GB:en
# more environment variables ...
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
# ^^ doesn't include my Pipenv path

so in fact, sudo -E was not passing $PATH. To fix this you can then see this answer on a similar question. Essentially you just add

Defaults env_reset
Defaults env_keep += "PATH PYTHONPATH"

to your sudoers file with visudo.