DataDog/dd-agent — pull request #1125 by isaacdd (2014-09-20 15:32:24+00:00)
Title: io_counters method is an psutil 2.1.2 method, get_io_counters

Documentation (http://docs.datadoghq.com/integrations/process/)
recommends using psutil 1.2.1 which uses get_io_counters.
io_counters is a 2.1.2 method. This tries both methods to make sure it
works on both versions.