python - Pip install won't install anything "No command by the name pip install" -

randomly seems pip has stopped working following error inside new virtualenv:

$ pip install requests==2.6.0 usage: pip command [options] no command name pip install   (maybe meant "pip install requests==2.6.0") 

i've tried following:

• creating new virtualenv
• reinstalling virtualenv
• reinstalling pip
• reinstalling python
• checking out repo again

which doesn't seem change anything, has else ran issue before?

note can pip install outside virtualenv.