Detect multiple versions of oj command

[kmyk]

Description

Some users install online-judge-tools package at many places (e.g., ~/.local, /usr/local, venv, pyenv, virtualenv, Anaconda, pipenv, etc.) (this is a mistake of users) and/or install multiple versions of the online-judge-tools package even at one place (a issue of pip command?). This prevents upgrading packages, because some old versions may hide the newest version.
We should detect such states and warn users.

Possible implementations and the analysis

• For the issue of multiple locations: searching $PATH (and some typical paths) for oj commands or oj-api commands. This is straightforward.
• For the issue of multiple versions: investigation is needed. I don't know why this happens and whether it's actually problematic. We should make a repro at first.
• Find an existing tool for this issue?

Other notes

• examples:
  • oj-verify が手元で動かない verification-helper#252
  • https://twitter.com/constant_drops/status/1320792346330460161