Library for running asynchronous parallel SSH commands over many hosts.
parallel-ssh uses asychronous network requests - there is no multi-threading or
multi-processing used.
This is a requirement for commands on many (hundreds/thousands/hundreds of
thousands) of hosts which would grind a system to a halt simply by having so
many processes/threads all wanting to execute if done with
multi-threading/processing.
Python 3 version.
