After upgrading to macOS v10.15 (Catalina), and upgrading all my vEnv modules, pip3 stopped working (gave error: "TypeError: 'module' object is not callable").
I found question 58386953 which led to here and solution.
sudo python3 -m pip uninstall pip
(this is necessary, but it did not fix problem, because it removed the base Python pip, but it didn't touch my vEnv pip)sudo easy_install pip
(reinstalling pip in base Python, not in vEnv)vEnv/bin
and type "source activate" to get into vEnvrm pip pip3 pip3.6
(it seems to be the only way to get rid of the bogus pip's in vEnv)