Return descriptive errors from is_app_available()
Return descriptive errors from is_app_available()

beni55/rebar-1,zugolosian/rebar3,jbalint/rebar3,norton/rebar3,vladdu/rebar3,rebar/rebar,beni55/rebar-1,scatterbrain/rebar,jacktang/rebar,benoitc/rebar3,paulo-ferraz-oliveira/rebar,heroku/rebar,sile/rebar3,choptastic/rebar,syl20bnr/rebar,matwey/rebar,beni55/rebar,dcarastan/rebar,RubberCthulhu/rebar,paulo-ferraz-oliveira/rebar,blt/rebar3,beni55/rebar,bsmr-erlang/rebar,dcarastan/rebar,lrascao/rebar3,tsloughter/rebar3,rebar/rebar,lrascao/rebar,wcy123/rebar,lpgauth/rebar,scatterbrain/rebar,norton/rebar,processone/rebar3,choptastic/rebar,saleyn/rebar3,jacktang/rebar,apache/couchdb-rebar,CMoH/rebar,apache/couchdb-rebar,linearregression/rebar3,syl20bnr/rebar,macintux/rebar,K2InformaticsGmbH/rebar,shkumagai/rebar,kellymclaughlin/rebar3,thomasbhatia/rebar,bsmr-erlang/rebar,oubiwann/rebar,oubiwann/rebar,erlang/rebar3,apache/couchdb-rebar,thomasbhatia/rebar,GabrielNicolasAvellaneda/rebar,project-fifo/rebar3,norton/rebar,fabiankrol/rebar3,RubberCthulhu/rebar,evnix/rebar,platinumthinker/rebar,cloudant/couchdb-rebar,fabiankrol/rebar3,csyangchen/rebar,K2InformaticsGmbH/rebar,macintux/rebar,SiDen/rebar,K2InformaticsGmbH/rebar,beni55/rebar,cloudant/couchdb-rebar,deadok22/rebar,bsmr-erlang/rebar,thomasbhatia/rebar,blt/rebar3,dcarastan/rebar,ferd/rebar3,wcy123/rebar,basho/rebar,heroku/rebar,rebar/rebar3,cloudant/couchdb-rebar,evnix/rebar,walrusVision/rebar3,zugolosian/rebar3,matwey/rebar,lrascao/rebar,platinumthinker/rebar,walrusVision/rebar3,bsmr-erlang/rebar,fauxsoup/rebar3,shkumagai/rebar,SiDen/rebar,lrascao/rebar,csyangchen/rebar,deadok22/rebar,jacktang/rebar,basho/rebar,oubiwann/rebar,benoitc/rebar3,GabrielNicolasAvellaneda/rebar,fishcakez/rebar3,processone/rebar3,fauxsoup/rebar3,platinumthinker/rebar,sile/rebar3,evnix/rebar,rebar/rebar,rebar/rebar3,syl20bnr/rebar,lrascao/rebar,K2InformaticsGmbH/rebar,shkumagai/rebar,norton/rebar,csyangchen/rebar,K2InformaticsGmbH/rebar,matwey/rebar,lrascao/rebar,surik/rebar3,surik/rebar3,jbalint/rebar3,norton/rebar,choptastic/rebar,matwey/rebar,GabrielNicolasAvellaneda/rebar,macintux/rebar,CMoH/rebar,lpgauth/rebar,linearregression/rebar3,paulo-ferraz-oliveira/rebar,scatterbrain/rebar,djnym/rebar3,lpgauth/rebar,project-fifo/rebar3,matwey/rebar,CMoH/rebar,SiDen/rebar