15848 - plugin application should give better errors for unknown plugins
15848 - plugin application should give better errors for unknown plugins

In the past running 'mco plugin doc undefinedplugin' would raise an
obscure error.

The error message has been fixed to better reflect that the plugin
could not be found.

ripienaar/marionette-collective,melissa/marionette-collective,richardc/marionette-collective,shrug/marionette-collective,melissa/marionette-collective,MikaelSmith/marionette-collective,spandeyindia/marionette-collective-1,heathseals/marionette-collective,spandeyindia/marionette-collective-1,pimpajr/marionette-collective,pimpajr/marionette-collective,ploubser/marionette-collective,johnduarte/marionette-collective,pimpajr/marionette-collective,pimpajr/marionette-collective,shrug/marionette-collective,geoffnichols/marionette-collective,Iristyle/marionette-collective,puppetlabs/marionette-collective,Iristyle/marionette-collective,shrug/marionette-collective,richardc/marionette-collective,MikaelSmith/marionette-collective,spandeyindia/marionette-collective-1,pimpajr/marionette-collective,MikaelSmith/marionette-collective,richardc/marionette-collective,ploubser/marionette-collective,melissa/marionette-collective,kbarber/marionette-collective,geoffnichols/marionette-collective,ripienaar/marionette-collective,spandeyindia/marionette-collective-1,pimpajr/marionette-collective,puppetlabs/marionette-collective,heathseals/marionette-collective,johnduarte/marionette-collective,ploubser/marionette-collective,johnduarte/marionette-collective,johnduarte/marionette-collective,Iristyle/marionette-collective,puppetlabs/marionette-collective,kbarber/marionette-collective,Iristyle/marionette-collective,johnduarte/marionette-collective,spandeyindia/marionette-collective-1,ripienaar/marionette-collective,MikaelSmith/marionette-collective,geoffnichols/marionette-collective,ripienaar/marionette-collective,shrug/marionette-collective,jessereynolds/marionette-collective,heathseals/marionette-collective,geoffnichols/marionette-collective,kbarber/marionette-collective,jessereynolds/marionette-collective,puppetlabs/marionette-collective,richardc/marionette-collective,ploubser/marionette-collective,Iristyle/marionette-collective,kbarber/marionette-collective,puppetlabs/marionette-collective,MikaelSmith/marionette-collective,richardc/marionette-collective,jessereynolds/marionette-collective,kbarber/marionette-collective,heathseals/marionette-collective,shrug/marionette-collective,heathseals/marionette-collective,MikaelSmith/marionette-collective,johnduarte/marionette-collective,geoffnichols/marionette-collective,melissa/marionette-collective,jessereynolds/marionette-collective,ripienaar/marionette-collective,kbarber/marionette-collective,jessereynolds/marionette-collective,richardc/marionette-collective,heathseals/marionette-collective,spandeyindia/marionette-collective-1,Iristyle/marionette-collective,puppetlabs/marionette-collective,melissa/marionette-collective,jessereynolds/marionette-collective,ploubser/marionette-collective,shrug/marionette-collective