buck_repo.py: Don't suppress subcommand output on error.
buck_repo.py: Don't suppress subcommand output on error.

Summary:
In several cases in our buck python wrappers, we'd mute the stdout
and stderr subcommands to presumably avoid noise in the common case.
However, this makes it difficult to diagnose issues/errors in those
subcommands (especially via automated build logs).

This diff removes the use of `DEV_NULL` and captures the output
using `subprocess.check_output`, which we print only in the error
case.

Test Plan: Ran locally.

luiseduardohdbackup/buck,Distrotech/buck,JoelMarcey/buck,artiya4u/buck,robbertvanginkel/buck,artiya4u/buck,marcinkwiatkowski/buck,rowillia/buck,liuyang-li/buck,zhan-xiong/buck,rhencke/buck,lukw00/buck,mnuessler/buck,raviagarwal7/buck,dsyang/buck,facebook/buck,justinmuller/buck,OkBuilds/buck,davido/buck,mikekap/buck,justinmuller/buck,rhencke/buck,1yvT0s/buck,robbertvanginkel/buck,brettwooldridge/buck,shybovycha/buck,mread/buck,liuyang-li/buck,OkBuilds/buck,clonetwin26/buck,LegNeato/buck,robbertvanginkel/buck,mnuessler/buck,1yvT0s/buck,rhencke/buck,sdwilsh/buck,Addepar/buck,OkBuilds/buck,dpursehouse/buck,vine/buck,zhan-xiong/buck,rhencke/buck,neonichu/buck,LegNeato/buck,grumpyjames/buck,Dominator008/buck,shs96c/buck,LegNeato/buck,rowillia/buck,OkBuilds/buck,LegNeato/buck,facebook/buck,ilya-klyuchnikov/buck,stuhood/buck,mread/buck,justinmuller/buck,Distrotech/buck,Distrotech/buck,davido/buck,shybovycha/buck,bocon13/buck,OkBuilds/buck,k21/buck,illicitonion/buck,vschs007/buck,liuyang-li/buck,Dominator008/buck,OkBuilds/buck,justinmuller/buck,clonetwin26/buck,ilya-klyuchnikov/buck,sdwilsh/buck,daedric/buck,shybovycha/buck,OkBuilds/buck,ilya-klyuchnikov/buck,shs96c/buck,dsyang/buck,nguyentruongtho/buck,mnuessler/buck,1yvT0s/buck,lukw00/buck,liuyang-li/buck,mogers/buck,Dominator008/buck,brettwooldridge/buck,Dominator008/buck,liuyang-li/buck,vschs007/buck,shs96c/buck,SeleniumHQ/buck,darkforestzero/buck,shybovycha/buck,rmaz/buck,vschs007/buck,mogers/buck,grumpyjames/buck,facebook/buck,JoelMarcey/buck,stuhood/buck,shs96c/buck,romanoid/buck,ilya-klyuchnikov/buck,robbertvanginkel/buck,zpao/buck,neonichu/buck,tgummerer/buck,bocon13/buck,rowillia/buck,SeleniumHQ/buck,vschs007/buck,vine/buck,dushmis/buck,lukw00/buck,artiya4u/buck,luiseduardohdbackup/buck,vschs007/buck,daedric/buck,pwz3n0/buck,dushmis/buck,Learn-Android-app/buck,robbertvanginkel/buck,liuyang-li/buck,JoelMarcey/buck,bocon13/buck,robbertvanginkel/buck,pwz3n0/buck,Dominator008/buck,hgl888/buck,rmaz/buck,romanoid/buck,Addepar/buck,kageiit/buck,darkforestzero/buck,dsyang/buck,romanoid/buck,stuhood/buck,grumpyjames/buck,mogers/buck,ilya-klyuchnikov/buck,vine/buck,nguyentruongtho/buck,ilya-klyuchnikov/buck,artiya4u/buck,liuyang-li/buck,shybovycha/buck,Learn-Android-app/buck,bocon13/buck,daedric/buck,liuyang-li/buck,dsyang/buck,grumpyjames/buck,JoelMarcey/buck,ilya-klyuchnikov/buck,luiseduardohdbackup/buck,daedric/buck,clonetwin26/buck,k21/buck,marcinkwiatkowski/buck,zhan-xiong/buck,pwz3n0/buck,k21/buck,darkforestzero/buck,shs96c/buck,davido/buck,Distrotech/buck,daedric/buck,facebook/buck,raviagarwal7/buck,zhan-xiong/buck,mikekap/buck,daedric/buck,ilya-klyuchnikov/buck,SeleniumHQ/buck,JoelMarcey/buck,Dominator008/buck,rhencke/buck,dushmis/buck,Heart2009/buck,hgl888/buck,Addepar/buck,Heart2009/buck,shs96c/buck,artiya4u/buck,liuyang-li/buck,Learn-Android-app/buck,pwz3n0/buck,janicduplessis/buck,SeleniumHQ/buck,shs96c/buck,zhan-xiong/buck,grumpyjames/buck,SeleniumHQ/buck,davido/buck,davido/buck,mogers/buck,artiya4u/buck,romanoid/buck,luiseduardohdbackup/buck,janicduplessis/buck,OkBuilds/buck,MarkRunWu/buck,neonichu/buck,robbertvanginkel/buck,MarkRunWu/buck,zpao/buck,Heart2009/buck,mread/buck,artiya4u/buck,Learn-Android-app/buck,neonichu/buck,sdwilsh/buck,darkforestzero/buck,davido/buck,OkBuilds/buck,zhuxiaohao/buck,grumpyjames/buck,raviagarwal7/buck,robbertvanginkel/buck,vine/buck,robbertvanginkel/buck,stuhood/buck,Dominator008/buck,Addepar/buck,pwz3n0/buck,dpursehouse/buck,pwz3n0/buck,romanoid/buck,SeleniumHQ/buck,shs96c/buck,Dominator008/buck,dsyang/buck,illicitonion/buck,ilya-klyuchnikov/buck,vine/buck,stuhood/buck,dsyang/buck,tgummerer/buck,1yvT0s/buck,mogers/buck,Heart2009/buck,justinmuller/buck,Heart2009/buck,justinmuller/buck,brettwooldridge/buck,Addepar/buck,JoelMarcey/buck,tgummerer/buck,bocon13/buck,mikekap/buck,vschs007/buck,robbertvanginkel/buck,shs96c/buck,mogers/buck,1yvT0s/buck,brettwooldridge/buck,SeleniumHQ/buck,janicduplessis/buck,LegNeato/buck,darkforestzero/buck,zhuxiaohao/buck,rhencke/buck,rmaz/buck,kageiit/buck,k21/buck,Learn-Android-app/buck,neonichu/buck,illicitonion/buck,daedric/buck,rmaz/buck,hgl888/buck,SeleniumHQ/buck,shs96c/buck,Distrotech/buck,romanoid/buck,clonetwin26/buck,justinmuller/buck,zhuxiaohao/buck,shybovycha/buck,rmaz/buck,mikekap/buck,vschs007/buck,davido/buck,Addepar/buck,janicduplessis/buck,janicduplessis/buck,darkforestzero/buck,mogers/buck,neonichu/buck,mnuessler/buck,kageiit/buck,stuhood/buck,facebook/buck,LegNeato/buck,JoelMarcey/buck,mnuessler/buck,ilya-klyuchnikov/buck,Distrotech/buck,JoelMarcey/buck,raviagarwal7/buck,rowillia/buck,dushmis/buck,mread/buck,mnuessler/buck,liuyang-li/buck,Learn-Android-app/buck,sdwilsh/buck,raviagarwal7/buck,marcinkwiatkowski/buck,tgummerer/buck,tgummerer/buck,siddhartharay007/buck,stuhood/buck,MarkRunWu/buck,illicitonion/buck,dpursehouse/buck,raviagarwal7/buck,JoelMarcey/buck,Distrotech/buck,stuhood/buck,sdwilsh/buck,siddhartharay007/buck,romanoid/buck,siddhartharay007/buck,lukw00/buck,dsyang/buck,marcinkwiatkowski/buck,mnuessler/buck,illicitonion/buck,mikekap/buck,sdwilsh/buck,vschs007/buck,nguyentruongtho/buck,lukw00/buck,bocon13/buck,romanoid/buck,nguyentruongtho/buck,marcinkwiatkowski/buck,janicduplessis/buck,siddhartharay007/buck,rmaz/buck,rhencke/buck,grumpyjames/buck,Addepar/buck,Learn-Android-app/buck,kageiit/buck,brettwooldridge/buck,clonetwin26/buck,facebook/buck,justinmuller/buck,darkforestzero/buck,marcinkwiatkowski/buck,vschs007/buck,sdwilsh/buck,justinmuller/buck,LegNeato/buck,vine/buck,dsyang/buck,clonetwin26/buck,Learn-Android-app/buck,tgummerer/buck,mread/buck,brettwooldridge/buck,artiya4u/buck,zhuxiaohao/buck,Dominator008/buck,lukw00/buck,grumpyjames/buck,justinmuller/buck,rowillia/buck,artiya4u/buck,artiya4u/buck,darkforestzero/buck,dushmis/buck,sdwilsh/buck,darkforestzero/buck,1yvT0s/buck,mogers/buck,bocon13/buck,LegNeato/buck,MarkRunWu/buck,rowillia/buck,1yvT0s/buck,mread/buck,sdwilsh/buck,nguyentruongtho/buck,liuyang-li/buck,rowillia/buck,rhencke/buck,pwz3n0/buck,mogers/buck,OkBuilds/buck,mnuessler/buck,LegNeato/buck,OkBuilds/buck,shybovycha/buck,nguyentruongtho/buck,SeleniumHQ/buck,brettwooldridge/buck,Learn-Android-app/buck,robbertvanginkel/buck,Heart2009/buck,Distrotech/buck,mogers/buck,janicduplessis/buck,romanoid/buck,siddhartharay007/buck,k21/buck,shybovycha/buck,luiseduardohdbackup/buck,illicitonion/buck,janicduplessis/buck,OkBuilds/buck,OkBuilds/buck,pwz3n0/buck,shybovycha/buck,marcinkwiatkowski/buck,Distrotech/buck,SeleniumHQ/buck,stuhood/buck,siddhartharay007/buck,1yvT0s/buck,neonichu/buck,clonetwin26/buck,vschs007/buck,vschs007/buck,dushmis/buck,lukw00/buck,mikekap/buck,daedric/buck,siddhartharay007/buck,mikekap/buck,zhan-xiong/buck,robbertvanginkel/buck,Dominator008/buck,zhan-xiong/buck,MarkRunWu/buck,grumpyjames/buck,raviagarwal7/buck,JoelMarcey/buck,rowillia/buck,rmaz/buck,hgl888/buck,Heart2009/buck,davido/buck,illicitonion/buck,neonichu/buck,LegNeato/buck,tgummerer/buck,rmaz/buck,Distrotech/buck,mikekap/buck,rowillia/buck,romanoid/buck,ilya-klyuchnikov/buck,rmaz/buck,illicitonion/buck,darkforestzero/buck,LegNeato/buck,hgl888/buck,romanoid/buck,JoelMarcey/buck,tgummerer/buck,MarkRunWu/buck,kageiit/buck,clonetwin26/buck,davido/buck,neonichu/buck,hgl888/buck,rmaz/buck,brettwooldridge/buck,dushmis/buck,robbertvanginkel/buck,zpao/buck,zpao/buck,vine/buck,k21/buck,clonetwin26/buck,vine/buck,Learn-Android-app/buck,zhuxiaohao/buck,dsyang/buck,brettwooldridge/buck,zhan-xiong/buck,dsyang/buck,lukw00/buck,k21/buck,k21/buck,dpursehouse/buck,Heart2009/buck,tgummerer/buck,lukw00/buck,zhan-xiong/buck,k21/buck,kageiit/buck,MarkRunWu/buck,dpursehouse/buck,bocon13/buck,MarkRunWu/buck,grumpyjames/buck,Dominator008/buck,shs96c/buck,LegNeato/buck,mikekap/buck,shybovycha/buck,tgummerer/buck,justinmuller/buck,shybovycha/buck,marcinkwiatkowski/buck,rowillia/buck,dsyang/buck,k21/buck,grumpyjames/buck,raviagarwal7/buck,rowillia/buck,daedric/buck,marcinkwiatkowski/buck,hgl888/buck,Addepar/buck,zhuxiaohao/buck,hgl888/buck,Heart2009/buck,k21/buck,zhan-xiong/buck,rhencke/buck,bocon13/buck,brettwooldridge/buck,grumpyjames/buck,dushmis/buck,mnuessler/buck,clonetwin26/buck,hgl888/buck,darkforestzero/buck,rowillia/buck,rmaz/buck,dpursehouse/buck,dushmis/buck,daedric/buck,bocon13/buck,shybovycha/buck,zhan-xiong/buck,kageiit/buck,Learn-Android-app/buck,Addepar/buck,davido/buck,pwz3n0/buck,janicduplessis/buck,vine/buck,janicduplessis/buck,artiya4u/buck,brettwooldridge/buck,mikekap/buck,justinmuller/buck,clonetwin26/buck,luiseduardohdbackup/buck,facebook/buck,raviagarwal7/buck,vine/buck,Addepar/buck,tgummerer/buck,raviagarwal7/buck,stuhood/buck,illicitonion/buck,shybovycha/buck,dpursehouse/buck,daedric/buck,SeleniumHQ/buck,justinmuller/buck,sdwilsh/buck,nguyentruongtho/buck,zpao/buck,siddhartharay007/buck,Addepar/buck,vine/buck,darkforestzero/buck,pwz3n0/buck,JoelMarcey/buck,luiseduardohdbackup/buck,brettwooldridge/buck,marcinkwiatkowski/buck,illicitonion/buck,sdwilsh/buck,Distrotech/buck,raviagarwal7/buck,daedric/buck,janicduplessis/buck,illicitonion/buck,marcinkwiatkowski/buck,LegNeato/buck,bocon13/buck,bocon13/buck,stuhood/buck,daedric/buck,lukw00/buck,ilya-klyuchnikov/buck,1yvT0s/buck,rhencke/buck,shs96c/buck,darkforestzero/buck,rmaz/buck,davido/buck,dsyang/buck,siddhartharay007/buck,zhuxiaohao/buck,marcinkwiatkowski/buck,mogers/buck,SeleniumHQ/buck,dushmis/buck,dsyang/buck,janicduplessis/buck,clonetwin26/buck,raviagarwal7/buck,k21/buck,Dominator008/buck,marcinkwiatkowski/buck,luiseduardohdbackup/buck,sdwilsh/buck,Addepar/buck,ilya-klyuchnikov/buck,rmaz/buck,davido/buck,mikekap/buck,dpursehouse/buck,vschs007/buck,romanoid/buck,raviagarwal7/buck,clonetwin26/buck,rhencke/buck,davido/buck,vschs007/buck,shs96c/buck,sdwilsh/buck,romanoid/buck,luiseduardohdbackup/buck,zhan-xiong/buck,zhan-xiong/buck,k21/buck,brettwooldridge/buck,Addepar/buck,SeleniumHQ/buck,zhuxiaohao/buck,pwz3n0/buck,illicitonion/buck,lukw00/buck,zhuxiaohao/buck,zpao/buck,zpao/buck,mikekap/buck,JoelMarcey/buck,illicitonion/buck