Make run_pip() return a single value and properly document it
Make run_pip() return a single value and properly document it

matysek/pip-accel,matysek/pip-accel,theyoprst/pip-accel,pombredanne/pip-accel,paylogic/pip-accel,paylogic/pip-accel,theyoprst/pip-accel,pombredanne/pip-accel