Hi Tim,

I just upgraded to 2.0 and was so damn impressed with upgrade code. I run Zulip in a VM with an NFS root, and hit some random NFS bug that resulted in this error:

... Found existing installation: cryptography 2.3 Uninstalling cryptography-2.3: Successfully uninstalled cryptography-2.3 Could not install packages due to an EnvironmentError: [Errno 16] Device or resource busy: '.nfs00000000016cef5200000f9e'

... `pip install` failed; retrying... ...

Then it succeeded, all by itself.