Installation on Mac
Trying to run virtualenv, @zeng gets:
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProtocolError('Connection aborted.', OSError(0, 'Error'))': /simple/virtualenv/
ERROR: Could not find a version that satisfies the requirement virtualenv (from versions: none)
ERROR: No matching distribution found for virtualenv