Messing up with python modules

I am really ashamed to ask this, but I stuck.
I want to run OpenNMT REST server.
I think, I messed up with my python versions.
It is easier to show problem:

me@mypc$ ./ --ip --port 4200
Traceback (most recent call last):
  File "./", line 2, in <module>
    import configargparse
ImportError: No module named configargparse

me@mypc$ /usr/bin/env python /usr/bin/pip3 install ConfigArgParse
Traceback (most recent call last):
  File "/usr/bin/pip3", line 9, in <module>
    from pip import main
ImportError: No module named pip

So, I am not sure what to do. Of course I have already installed python3-pip (with apt install).

Did you try by running pip3 directly?

If this does not work it looks like you pip installation is broken. You won’t get much help on the OpenNMT forum.