Hmm CourageousLizard33 seems you stumbled on a weird bug,
This piece of code only tries to get the username of the current UID, but since you are running inside a docker and probably set the environment UID but there is no "actual" UID by that number on /etc/passwd , and so it cannot resolve it.
I'm attaching a quick fix, please let me know if it solved the problem.
I'd like to make sure we have it in the next RC as soon as possible.