Improve Buck python wrapper UI when Nailgun client raises an exception
Improve Buck python wrapper UI when Nailgun client raises an exception

Summary: Does what it says on the tin.

Test Plan: `buck build buck`, kill Java, confirm UI doesn't include
stack trace

Reviewed By: sdwilsh

fb-gh-sync-id: a6243be

SeleniumHQ/buck,Addepar/buck,rowillia/buck,kageiit/buck,justinmuller/buck,illicitonion/buck,raviagarwal7/buck,dsyang/buck,mikekap/buck,bocon13/buck,JoelMarcey/buck,OkBuilds/buck,rowillia/buck,mogers/buck,dsyang/buck,justinmuller/buck,grumpyjames/buck,mogers/buck,liuyang-li/buck,marcinkwiatkowski/buck,shs96c/buck,darkforestzero/buck,shybovycha/buck,robbertvanginkel/buck,liuyang-li/buck,Distrotech/buck,rmaz/buck,grumpyjames/buck,zhan-xiong/buck,kageiit/buck,janicduplessis/buck,Dominator008/buck,mikekap/buck,Distrotech/buck,raviagarwal7/buck,shs96c/buck,Addepar/buck,justinmuller/buck,zhan-xiong/buck,shs96c/buck,LegNeato/buck,SeleniumHQ/buck,romanoid/buck,liuyang-li/buck,clonetwin26/buck,Addepar/buck,zhan-xiong/buck,shs96c/buck,dsyang/buck,marcinkwiatkowski/buck,romanoid/buck,darkforestzero/buck,Addepar/buck,sdwilsh/buck,SeleniumHQ/buck,illicitonion/buck,sdwilsh/buck,zhan-xiong/buck,brettwooldridge/buck,k21/buck,vschs007/buck,davido/buck,sdwilsh/buck,Addepar/buck,dsyang/buck,rmaz/buck,raviagarwal7/buck,vine/buck,raviagarwal7/buck,OkBuilds/buck,zhan-xiong/buck,shybovycha/buck,OkBuilds/buck,robbertvanginkel/buck,brettwooldridge/buck,clonetwin26/buck,Addepar/buck,SeleniumHQ/buck,vschs007/buck,ilya-klyuchnikov/buck,clonetwin26/buck,dsyang/buck,robbertvanginkel/buck,vschs007/buck,marcinkwiatkowski/buck,janicduplessis/buck,darkforestzero/buck,liuyang-li/buck,zpao/buck,vschs007/buck,justinmuller/buck,clonetwin26/buck,nguyentruongtho/buck,justinmuller/buck,daedric/buck,raviagarwal7/buck,Dominator008/buck,rmaz/buck,sdwilsh/buck,illicitonion/buck,robbertvanginkel/buck,liuyang-li/buck,brettwooldridge/buck,mogers/buck,SeleniumHQ/buck,Distrotech/buck,kageiit/buck,OkBuilds/buck,robbertvanginkel/buck,zpao/buck,davido/buck,liuyang-li/buck,vine/buck,dsyang/buck,marcinkwiatkowski/buck,vine/buck,raviagarwal7/buck,nguyentruongtho/buck,Addepar/buck,OkBuilds/buck,JoelMarcey/buck,davido/buck,LegNeato/buck,davido/buck,illicitonion/buck,LegNeato/buck,romanoid/buck,bocon13/buck,k21/buck,sdwilsh/buck,marcinkwiatkowski/buck,shybovycha/buck,ilya-klyuchnikov/buck,davido/buck,grumpyjames/buck,OkBuilds/buck,JoelMarcey/buck,vine/buck,janicduplessis/buck,janicduplessis/buck,justinmuller/buck,zhan-xiong/buck,clonetwin26/buck,marcinkwiatkowski/buck,kageiit/buck,mikekap/buck,rmaz/buck,illicitonion/buck,LegNeato/buck,bocon13/buck,robbertvanginkel/buck,zhan-xiong/buck,rmaz/buck,sdwilsh/buck,dsyang/buck,vine/buck,mikekap/buck,k21/buck,romanoid/buck,darkforestzero/buck,rmaz/buck,darkforestzero/buck,facebook/buck,dsyang/buck,Distrotech/buck,clonetwin26/buck,sdwilsh/buck,JoelMarcey/buck,kageiit/buck,JoelMarcey/buck,sdwilsh/buck,raviagarwal7/buck,rowillia/buck,vine/buck,darkforestzero/buck,SeleniumHQ/buck,darkforestzero/buck,shybovycha/buck,vschs007/buck,dsyang/buck,mikekap/buck,shybovycha/buck,k21/buck,ilya-klyuchnikov/buck,grumpyjames/buck,vine/buck,OkBuilds/buck,kageiit/buck,sdwilsh/buck,rowillia/buck,justinmuller/buck,rowillia/buck,janicduplessis/buck,daedric/buck,rmaz/buck,raviagarwal7/buck,OkBuilds/buck,ilya-klyuchnikov/buck,OkBuilds/buck,rmaz/buck,Addepar/buck,marcinkwiatkowski/buck,rowillia/buck,nguyentruongtho/buck,zhan-xiong/buck,mikekap/buck,k21/buck,shybovycha/buck,shs96c/buck,vine/buck,SeleniumHQ/buck,SeleniumHQ/buck,zpao/buck,bocon13/buck,davido/buck,illicitonion/buck,janicduplessis/buck,romanoid/buck,marcinkwiatkowski/buck,shs96c/buck,SeleniumHQ/buck,Distrotech/buck,darkforestzero/buck,brettwooldridge/buck,romanoid/buck,zpao/buck,liuyang-li/buck,vschs007/buck,clonetwin26/buck,Dominator008/buck,robbertvanginkel/buck,sdwilsh/buck,facebook/buck,OkBuilds/buck,JoelMarcey/buck,davido/buck,JoelMarcey/buck,ilya-klyuchnikov/buck,LegNeato/buck,brettwooldridge/buck,mikekap/buck,kageiit/buck,bocon13/buck,clonetwin26/buck,sdwilsh/buck,LegNeato/buck,grumpyjames/buck,romanoid/buck,daedric/buck,vschs007/buck,mikekap/buck,mogers/buck,zhan-xiong/buck,illicitonion/buck,shs96c/buck,zhan-xiong/buck,raviagarwal7/buck,romanoid/buck,Dominator008/buck,brettwooldridge/buck,shs96c/buck,zpao/buck,rowillia/buck,darkforestzero/buck,Distrotech/buck,shs96c/buck,mogers/buck,mikekap/buck,marcinkwiatkowski/buck,ilya-klyuchnikov/buck,clonetwin26/buck,illicitonion/buck,k21/buck,shybovycha/buck,vine/buck,mogers/buck,rowillia/buck,marcinkwiatkowski/buck,brettwooldridge/buck,romanoid/buck,justinmuller/buck,rowillia/buck,raviagarwal7/buck,brettwooldridge/buck,mogers/buck,justinmuller/buck,grumpyjames/buck,ilya-klyuchnikov/buck,davido/buck,darkforestzero/buck,darkforestzero/buck,janicduplessis/buck,brettwooldridge/buck,rmaz/buck,LegNeato/buck,Dominator008/buck,LegNeato/buck,marcinkwiatkowski/buck,zpao/buck,rowillia/buck,robbertvanginkel/buck,nguyentruongtho/buck,Addepar/buck,shybovycha/buck,janicduplessis/buck,grumpyjames/buck,justinmuller/buck,mikekap/buck,SeleniumHQ/buck,vine/buck,rmaz/buck,mogers/buck,liuyang-li/buck,facebook/buck,nguyentruongtho/buck,bocon13/buck,OkBuilds/buck,illicitonion/buck,vschs007/buck,OkBuilds/buck,clonetwin26/buck,janicduplessis/buck,Dominator008/buck,JoelMarcey/buck,daedric/buck,darkforestzero/buck,clonetwin26/buck,LegNeato/buck,raviagarwal7/buck,sdwilsh/buck,daedric/buck,mikekap/buck,OkBuilds/buck,k21/buck,Distrotech/buck,davido/buck,JoelMarcey/buck,liuyang-li/buck,Distrotech/buck,vschs007/buck,grumpyjames/buck,ilya-klyuchnikov/buck,dsyang/buck,shybovycha/buck,vine/buck,dsyang/buck,JoelMarcey/buck,Dominator008/buck,shs96c/buck,nguyentruongtho/buck,shs96c/buck,justinmuller/buck,grumpyjames/buck,marcinkwiatkowski/buck,Distrotech/buck,daedric/buck,bocon13/buck,LegNeato/buck,facebook/buck,k21/buck,romanoid/buck,bocon13/buck,Dominator008/buck,robbertvanginkel/buck,dsyang/buck,rmaz/buck,justinmuller/buck,zhan-xiong/buck,shybovycha/buck,raviagarwal7/buck,davido/buck,LegNeato/buck,facebook/buck,vschs007/buck,liuyang-li/buck,bocon13/buck,grumpyjames/buck,robbertvanginkel/buck,brettwooldridge/buck,janicduplessis/buck,Distrotech/buck,vschs007/buck,brettwooldridge/buck,romanoid/buck,daedric/buck,facebook/buck,ilya-klyuchnikov/buck,ilya-klyuchnikov/buck,ilya-klyuchnikov/buck,janicduplessis/buck,dsyang/buck,mogers/buck,rowillia/buck,clonetwin26/buck,zpao/buck,bocon13/buck,daedric/buck,illicitonion/buck,daedric/buck,k21/buck,romanoid/buck,mikekap/buck,romanoid/buck,justinmuller/buck,Dominator008/buck,Dominator008/buck,marcinkwiatkowski/buck,daedric/buck,mogers/buck,davido/buck,darkforestzero/buck,Addepar/buck,Addepar/buck,JoelMarcey/buck,JoelMarcey/buck,k21/buck,robbertvanginkel/buck,robbertvanginkel/buck,JoelMarcey/buck,Addepar/buck,Distrotech/buck,k21/buck,Dominator008/buck,illicitonion/buck,brettwooldridge/buck,davido/buck,shybovycha/buck,sdwilsh/buck,grumpyjames/buck,nguyentruongtho/buck,grumpyjames/buck,daedric/buck,robbertvanginkel/buck,SeleniumHQ/buck,mogers/buck,SeleniumHQ/buck,illicitonion/buck,bocon13/buck,bocon13/buck,Dominator008/buck,raviagarwal7/buck,davido/buck,clonetwin26/buck,rowillia/buck,rmaz/buck,ilya-klyuchnikov/buck,k21/buck,Addepar/buck,shs96c/buck,shybovycha/buck,daedric/buck,SeleniumHQ/buck,LegNeato/buck,illicitonion/buck,brettwooldridge/buck,rmaz/buck,ilya-klyuchnikov/buck,vschs007/buck,facebook/buck,liuyang-li/buck,shs96c/buck,shybovycha/buck,daedric/buck,zhan-xiong/buck,LegNeato/buck,vschs007/buck,k21/buck,janicduplessis/buck,zhan-xiong/buck