When I try to install anything with pip or pip3, I get:
pip
pip3
$ sudo pip3 install python3-tk Tra
Check wether you have an older version of requests sitting in your ~/.local/lib/python2.7/site-packages/ and remove it if it is the case (change path to reflect your python version). This solved the issue for me.
requests
~/.local/lib/python2.7/site-packages/