Drop --use-mirrors in call to pip
Drop --use-mirrors in call to pip

This option no longer exists in pip.

alisaifee/holmium.core,kejkz/holmium.core,alisaifee/holmium.core,alisaifee/holmium.core,alisaifee/holmium.core,kejkz/holmium.core,kejkz/holmium.core,kejkz/holmium.core