api: use errors package more
api: use errors package more

frankban/juju-tmp,mikemccracken/juju,macgreagoir/juju,sinzui/juju,tsakas/juju,howbazaar/juju,alesstimec/juju,cherylj/juju,mhilton/juju-juju,tych0/juju,fwereade/juju,sinzui/juju,reedobrien/juju,bz2/juju,cherylj/juju,dimitern/juju,dimitern/juju,frankban/juju-tmp,waigani/juju,gabriel-samfira/juju,ericsnowcurrently/juju,anastasiamac/juju,bac/juju,mjs/juju,marcmolla/juju,waigani/juju,fwereade/juju,Altoros/juju-cloudsigma,makyo/juju,macgreagoir/juju,AdamIsrael/juju,thomnico/juju,howbazaar/juju,frankban/juju-tmp,Altoros/juju-cloudsigma,frankban/juju,mhilton/juju-juju,AdamIsrael/juju,frankban/juju,thomnico/juju,AdamIsrael/juju,bz2/juju,alesstimec/juju,tasdomas/juju,voidspace/juju,mjs/juju,dimitern/juju,frankban/juju,marcmolla/juju,thomnico/juju,perrito666/juju,bogdanteleaga/juju,tych0/juju,mhilton/juju-juju,perrito666/juju,cloud-green/juju,thomnico/juju,howbazaar/juju,axw/juju,makyo/juju,Altoros/juju-cloudsigma,axw/juju,wwitzel3/juju,tych0/juju,tsakas/juju,axw/juju,frankban/juju,marcmolla/juju,dooferlad/juju,bac/juju,mikemccracken/juju,dimitern/juju,gabriel-samfira/juju,makyo/juju,anastasiamac/juju,bz2/juju,mjs/juju,reedobrien/juju,dooferlad/juju,bz2/juju,sinzui/juju,dooferlad/juju,ericsnowcurrently/juju,reedobrien/juju,gabriel-samfira/juju,gabriel-samfira/juju,marcmolla/juju,bogdanteleaga/juju,tsakas/juju,voidspace/juju,cherylj/juju,tych0/juju,kat-co/juju,wwitzel3/juju,bogdanteleaga/juju,kat-co/juju,bac/juju,waigani/juju,voidspace/juju,cloud-green/juju,mjs/juju,bac/juju,sinzui/juju,makyo/juju,mjs/juju,dooferlad/juju,axw/juju,mhilton/juju,tasdomas/juju,mjs/juju,mikemccracken/juju,alesstimec/juju,wwitzel3/juju,macgreagoir/juju,ericsnowcurrently/juju,davecheney/juju,perrito666/juju,alesstimec/juju,tsakas/juju,anastasiamac/juju,macgreagoir/juju,Altoros/juju-cloudsigma,howbazaar/juju,bogdanteleaga/juju,anastasiamac/juju,tasdomas/juju,reedobrien/juju,dooferlad/juju,cloud-green/juju,kat-co/juju,ericsnowcurrently/juju,kat-co/juju,bac/juju,bz2/juju,mhilton/juju,mjs/juju,cloud-green/juju,davecheney/juju,mikemccracken/juju,davecheney/juju,alesstimec/juju,kat-co/juju,AdamIsrael/juju,mhilton/juju,ericsnowcurrently/juju,frankban/juju-tmp,fwereade/juju,frankban/juju,perrito666/juju,perrito666/juju,mikemccracken/juju,tasdomas/juju,voidspace/juju,anastasiamac/juju,reedobrien/juju,davecheney/juju,gabriel-samfira/juju,mhilton/juju-juju,marcmolla/juju,macgreagoir/juju,axw/juju,wwitzel3/juju,waigani/juju,howbazaar/juju,mhilton/juju,fwereade/juju,dimitern/juju,cherylj/juju