Handle multiple concurrent pip processes on the same environment #2361
Description
I saw that pip 6 added file-based locking to the http cache to avoid multi-process contention. Something should be done to handle multiple packages being installed into the same virtualenv at the same time. For example if I had a concurrent makefile that installed independent foo_webapp1 and foo_webapp2 packages with a common dependency on foo_core, what would happen right now? What should happen? I guess the easiest is just to abort the second process.