I'm not sure what exactly this user is needed for, i.e. under what circumstances
it must exist or not, but creating it unconditionally seems like the wrong thing
to do. I complained to @offlinehacker about this on Github, but got no response
for a week or so. I'm disabling the extraUsers bit to put out the fire, and now
hope that someone who actually knows about Graphite implements a proper solution
later.