Rubygem: fix raising of CommandError for #install
Rubygem: fix raising of CommandError for #install

Fix issue #870 (gem-install seems broken on jruby)

nju520/pry,nju520/pry,jasonm23/pry,caporta/pry,josue804/debunker,jasnow/pry,printercu/pry,icebreaker/pry,nju520/pry,gfvcastro/pry,gfvcastro/pry,jasonm23/pry,raeno/pry,ooohiroyukiooo/pry,scalixte-mdsol/pry,pvdb/pry,geoffreylitt/pry,raeno/pry,tdg5/pry,sferik/pry,josue804/debunker,sideci-sample/sideci-sample-pry,85x14/pry,richo/pry,bronzdoc/pry,jasnow/pry,tdg5/pry,shockone/pry,jasonm23/pry,ngpestelos/pry,bronzdoc/pry,pvdb/pry,85x14/pry,ooohiroyukiooo/pry,raeno/pry,tdg5/pry,jasnow/pry,85x14/pry,scalixte-mdsol/pry,icebreaker/pry,geoffreylitt/pry,sferik/pry,ngpestelos/pry,caporta/pry,ooohiroyukiooo/pry,scalixte-mdsol/pry,caporta/pry,deivid-rodriguez/pry,printercu/pry,shockone/pry,shockone/pry