raise an error if problems detecting the bundler vendor directory
raise an error if problems detecting the bundler vendor directory

tomwolfe/heroku-buildpack-gsl-ruby,0x00evil/heroku-buildpack-ruby,zidekmat/buildpack-ruby,ndbroadbent/heroku-buildpack-turbo-sprockets,dlorson/gentle-buildpack,cloudControl/buildpack-ruby,gbenedict/heroku-buildpack-ruby,tpope/heroku-buildpack-ruby-tpope,musicglue/heroku-buildpack-ruby,ablease/custom-buildpack,hpcloud/ruby-buildpack,dleavitt/heroku-buildpack-ruby,rowanoulton/heroku-buildpack-ruby,andycroll/heroku-buildpack-jekyll,simonnordberg/heroku-buildpack-ruby,sky-uk/ruby-buildpack,mrhenry/heroku-buildpack-ruby,dtao/teeny-buildpack,trumaker/heroku-buildpack-turbo-sprockets,michaelphines/alexa-nest,takii/heroku-buildpack-ruby,ascot21/heroku-buildpack-turbo-sprockets,fcruxen/ruby-buildpack,tomwolfe/heroku-buildpack-gsl-ruby,jasonlevens/heroku-buildpack-ruby,jumptvs/BP_Ruby,electricobjects/heroku-buildpack-ruby,mperejda/heroku-buildpack-ruby,stefansundin/heroku-buildpack-ruby,erintherad/heroku-buildpack-ruby,hixi/heroku-buildpack-ruby,ericroberts/heroku-buildpack-ruby,jumptvs/BP_Ruby,musicglue/heroku-buildpack-ruby,shuber/heroku-buildpack-ruby,makifund/heroku-buildpack-ruby,hpcloud/ruby-buildpack,mattwalters/heroku-buildpack-ruby,Altoros/ruby-buildpack,daltonrenaldo/heroku-buildpack-ruby,stolt45/heroku-buildpack-ruby-with-sqlite3,cloudn/buildpack-ruby,ericboehs/heroku-buildpack-ruby,crdschurch/heroku-buildpack-ruby,takii/db2rubybuildpack,wakermahmud/heroku-buildpack-jekyll,cloudControl/buildpack-ruby,dtao/teeny-buildpack,ibmdb/db2rubybuildpack,ilpoldo/heroku-buildpack-ruby,cloudn/buildpack-ruby,bskyb-commerce/ruby-buildpack,packetmonkey/heroku-buildpack-ruby,jasonlevens/heroku-buildpack-ruby,Genius/heroku-buildpack-ruby,awebneck/heroku-buildpack-canvas,CPPWind/ruby-buildpack,dieze/heroku-buildpack-ruby-hooks,qnyp/heroku-buildpack-ruby-bower,swipesense/heroku-buildpack-ruby,beydogan/ruby-buildpack,Scalingo/ruby-buildpack,fcruxen/ruby-buildpack,codykrieger/heroku-buildpack-jekyll,blueapron/heroku-buildpack-ruby,cloudn/buildpack-ruby,jayshreeanand/heroku-buildpack-ruby,pietrop/heroku-buildpack-ruby,hpcloud/ruby-buildpack,samfrench/heroku-buildpack-ruby,hellojustin/heroku-buildpack-custom-ruby,jonseaberg/heroku-buildpack-turbo-sprockets,bwaite-jaroop/heroku-buildpack-ruby,mattmanning/heroku-buildpack-ruby-jekyll,gls1/heroku-buildpack-ruby-pdftk,orenyk/heroku-buildpack-ruby,mperejda/heroku-buildpack-ruby,erintherad/heroku-buildpack-ruby,wakermahmud/heroku-buildpack-jekyll,jumptvs/BP_Ruby,derrek/heroku-buildpack-ruby,hatofmonkeys/ruby-testing-buildpack,reesio/heroku-buildpack-ruby,DyegoCosta/heroku-buildpack-ruby,hellojustin/heroku-buildpack-custom-ruby,HYPERHYPER/heroku-buildpack-ruby,rvizza/heroku-buildpack-gsl-ruby,sky-uk/help-heroku-buildpack,diasks2/heroku-buildpack-mecab,qstream/heroku-buildpack-ruby,hpcloud/ruby-buildpack,ericroberts/heroku-buildpack-ruby,space150/heroku-buildpack-ruby,tenjikinc/heroku-buildpack-ruby,tenjikinc/heroku-buildpack-ruby,orlando/heroku-buildpack-ruby,d-reinhold/cf-buildpack-ruby,sstelfox/buildpack-ruby,daltonrenaldo/heroku-buildpack-ruby,zidekmat/buildpack-ruby,anay/buildpack-ruby-with-oracle-jdk,teodor-pripoae/heroku-buildpack-ruby,sky-uk/ruby-buildpack,rvizza/heroku-buildpack-gsl-ruby,takii/db2rubybuildpack,Altoros/ruby-buildpack,mattwalters/heroku-buildpack-ruby,fgbreel/heroku-buildpack-ruby,mrhenry/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,Micka33/heroku-buildpack-ruby-liblua,crdschurch/heroku-buildpack-ruby,vhx/heroku-buildpack,markaschneider/heroku-buildpack-ruby-ffmpeg-sox,iamjarvo/ruby-buildpack,diasks2/heroku-buildpack-mecab,stefansundin/heroku-buildpack-ruby,scottatron/moc-buildpack,cloudfoundry/ruby-buildpack,ilpoldo/heroku-buildpack-ruby,dieze/heroku-buildpack-ruby-hooks,guidance-guarantee-programme/heroku-buildpack-princexml-old,icelab/heroku-buildpack-ruby,sky-uk/ruby-buildpack,gls1/heroku-buildpack-ruby-pdftk-new,jonasoberschweiber/heroku-buildpack-ruby,brightbytes/heroku-buildpack-ruby-without-assets-precompile,anay/buildpack-ruby-with-oracle-jdk,donnykurnia/heroku-buildpack-ruby,hixi/heroku-buildpack-ruby,barakav/heroku-buildpack-ruby,dtao/deft-buildpack-ruby,bskyb-commerce/ruby-buildpack,tdenovan/heroku-buildpack-ruby,qstream/heroku-buildpack-ruby,mattmanning/heroku-buildpack-ruby-jekyll,bskyb-commerce/ruby-buildpack,hatofmonkeys/ruby-testing-buildpack,teodor-pripoae/heroku-buildpack-ruby,Jonty/ruby-buildpack,takii/heroku-buildpack-ruby,Jonty/ruby-buildpack,ndbroadbent/heroku-buildpack-turbo-sprockets,gbenedict/heroku-buildpack-ruby,ibmdb/db2rubybuildpack,cordata/heroku-buildpack-ruby,DigitalInnovation/heroku-buildpack-mslabs,Nedomas/heroku-buildpack-ruby-minus-node-with-node-paths,d-reinhold/cf-buildpack-ruby,CPPWind/ruby-buildpack,allomov/fat-free-heroku-buildpack-ruby,Git-Host/prelang-buildpack,Micka33/heroku-buildpack-ruby-liblua,moneyadviceservice/heroku-buildpack-ruby-bowndler,Dim25/heroku-buildpack-ruby-GSL,zoomer/heroku-buildpack-ruby-bower,orlando/heroku-buildpack-ruby,recursecenter/heroku-buildpack-ruby,lyoshenka/heroku-buildpack-ruby-jekyll,Scalingo/ruby-buildpack,bskyb-commerce/help-heroku-buildpack,ruby/heroku-buildpack-www-ruby-lang,engineyard/heroku-buildpack-ruby,sky-uk/help-heroku-buildpack,Genius/heroku-buildpack-ruby,jayshreeanand/heroku-buildpack-ruby,orenyk/heroku-buildpack-ruby,takii/db2rubybuildpack,pietrop/heroku-buildpack-ruby,awebneck/heroku-buildpack-canvas,ekaranto/rails4-bluemix-buildpack,Nedomas/heroku-buildpack-ruby-minus-node-with-node-paths,gls1/heroku-buildpack-ruby-pdftk-new,ekaranto/rails4-bluemix-buildpack,ascot21/heroku-buildpack-turbo-sprockets,beydogan/ruby-buildpack,hatofmonkeys/ruby-testing-buildpack,sstelfox/buildpack-ruby,allomov/fat-free-heroku-buildpack-ruby,guidance-guarantee-programme/heroku-buildpack-princexml-old,dlorson/gentle-buildpack,amaltson/heroku-buildpack-ruby,makifund/heroku-buildpack-ruby,bskyb-commerce/help-heroku-buildpack,bellycard/heroku-buildpack-ruby,pkgr/heroku-buildpack-ruby,iamjarvo/ruby-buildpack,fgbreel/heroku-buildpack-ruby,cloudn/buildpack-ruby,aarongray/heroku-buildpack-ruby,schu/buildpack-testing,Altoros/ruby-buildpack,redhotvengeance/heroku-buildpack-deep-thought,schu/buildpack-testing,simonnordberg/heroku-buildpack-ruby,jonseaberg/heroku-buildpack-turbo-sprockets,cloudfoundry/ruby-buildpack,moneyadviceservice/heroku-buildpack-ruby-bowndler,DigitalInnovation/heroku-buildpack-mslabs,packetmonkey/heroku-buildpack-ruby,fcruxen/ruby-buildpack,michaelphines/alexa-nest,swipesense/heroku-buildpack-ruby,fcruxen/ruby-buildpack,cmaggard/heroku-buildpack-turbo-sprockets,jgable/buildpack-ruby-rack-setup-tasks,stolt45/heroku-buildpack-ruby-with-sqlite3,iamjarvo/ruby-buildpack,righi/instacart-heroku-buildpack,icelab/heroku-buildpack-ruby,0x00evil/heroku-buildpack-ruby,ChefSteps/heroku-buildpack-ruby,takii/db2rubybuildpack,barakav/heroku-buildpack-ruby,ekaranto/rails4-bluemix-buildpack,dtao/deft-buildpack-ruby,iamjarvo/ruby-buildpack,jgable/buildpack-ruby-rack-setup-tasks,ericboehs/heroku-buildpack-ruby,jumptvs/BP_Ruby,markaschneider/heroku-buildpack-ruby-ffmpeg-sox,lyoshenka/heroku-buildpack-ruby-jekyll,reesio/heroku-buildpack-ruby,Jonty/ruby-buildpack,scottatron/moc-buildpack,ltrademark/heroku-buildpack-ruby,jonasoberschweiber/heroku-buildpack-ruby,aarongray/heroku-buildpack-ruby,codykrieger/heroku-buildpack-jekyll,rowanoulton/heroku-buildpack-ruby,righi/instacart-heroku-buildpack,catalyzeio/buildpack-ruby,ltrademark/heroku-buildpack-ruby,samfrench/heroku-buildpack-ruby,CPPWind/ruby-buildpack,DouglasAllen/heroku-buildpack-ruby,pilotcreative/heroku-buildpack-ruby,heroku/heroku-buildpack-ruby,ChefSteps/heroku-buildpack-ruby,d-reinhold/cf-buildpack-ruby,zunda/heroku-buildpack-ruby,CPPWind/ruby-buildpack,instacart/heroku-buildpack-ruby,instacart/heroku-buildpack-ruby,mintybit/heroku-buildpack-ruby,derrek/heroku-buildpack-ruby,bellycard/heroku-buildpack-ruby,donnykurnia/heroku-buildpack-ruby,engineyard/heroku-buildpack-ruby,Git-Host/prelang-buildpack,Dim25/heroku-buildpack-ruby-GSL,zunda/heroku-buildpack-ruby,ablease/custom-buildpack,brightbytes/heroku-buildpack-ruby-without-assets-precompile,zoomer/heroku-buildpack-ruby-bower,vhx/heroku-buildpack,ablease/custom-buildpack,schu/heroku-buildpack-ruby,shuber/heroku-buildpack-ruby,ekaranto/rails4-bluemix-buildpack,cloudfoundry/ruby-buildpack,cmaggard/heroku-buildpack-turbo-sprockets,amaltson/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,electricobjects/heroku-buildpack-ruby,Jonty/ruby-buildpack,sky-uk/ruby-buildpack,leonardykris/mos-ruby-buildpack,dleavitt/heroku-buildpack-ruby,KoanHealth/heroku-buildpack-marvin-setup,pilotcreative/heroku-buildpack-ruby,mintybit/heroku-buildpack-ruby,Altoros/ruby-buildpack,DouglasAllen/heroku-buildpack-ruby,space150/heroku-buildpack-ruby,blueapron/heroku-buildpack-ruby,bwaite-jaroop/heroku-buildpack-ruby,gls1/heroku-buildpack-ruby-pdftk,HYPERHYPER/heroku-buildpack-ruby,pkgr/heroku-buildpack-ruby,cordata/heroku-buildpack-ruby,heroku/heroku-buildpack-ruby,recursecenter/heroku-buildpack-ruby,bskyb-commerce/ruby-buildpack,trumaker/heroku-buildpack-turbo-sprockets,ablease/custom-buildpack,KoanHealth/heroku-buildpack-marvin-setup,leonardykris/mos-ruby-buildpack,schu/heroku-buildpack-ruby,ibmdb/db2rubybuildpack,redhotvengeance/heroku-buildpack-deep-thought,DyegoCosta/heroku-buildpack-ruby,andycroll/heroku-buildpack-jekyll,catalyzeio/buildpack-ruby,tdenovan/heroku-buildpack-ruby,tpope/heroku-buildpack-ruby-tpope,qnyp/heroku-buildpack-ruby-bower