Fix typo in `diff_rulekeys.py`
Fix typo in `diff_rulekeys.py`

Summary: String concatenation is annoying

Test Plan:
Run rule key differ with a bad input.

Before: KeyError: u'Left log does not contain {}. Did you forget toenable logging? (see help).'
After: KeyError: u'Left log does not contain {}. Did you forget to enable logging? (see help).'

Reviewed By: Coneko

fbshipit-source-id: 5e34953

zhan-xiong/buck,clonetwin26/buck,shybovycha/buck,shs96c/buck,Addepar/buck,shs96c/buck,shybovycha/buck,romanoid/buck,robbertvanginkel/buck,LegNeato/buck,JoelMarcey/buck,brettwooldridge/buck,JoelMarcey/buck,LegNeato/buck,rmaz/buck,shs96c/buck,JoelMarcey/buck,robbertvanginkel/buck,vschs007/buck,zhan-xiong/buck,clonetwin26/buck,rmaz/buck,romanoid/buck,k21/buck,shybovycha/buck,Addepar/buck,facebook/buck,shs96c/buck,marcinkwiatkowski/buck,brettwooldridge/buck,rmaz/buck,romanoid/buck,dsyang/buck,vschs007/buck,SeleniumHQ/buck,ilya-klyuchnikov/buck,marcinkwiatkowski/buck,rmaz/buck,kageiit/buck,ilya-klyuchnikov/buck,kageiit/buck,ilya-klyuchnikov/buck,brettwooldridge/buck,LegNeato/buck,brettwooldridge/buck,nguyentruongtho/buck,shybovycha/buck,shybovycha/buck,clonetwin26/buck,facebook/buck,dsyang/buck,Addepar/buck,dsyang/buck,romanoid/buck,ilya-klyuchnikov/buck,romanoid/buck,marcinkwiatkowski/buck,vschs007/buck,LegNeato/buck,zhan-xiong/buck,shs96c/buck,JoelMarcey/buck,ilya-klyuchnikov/buck,SeleniumHQ/buck,Addepar/buck,rmaz/buck,nguyentruongtho/buck,shybovycha/buck,ilya-klyuchnikov/buck,k21/buck,JoelMarcey/buck,zhan-xiong/buck,clonetwin26/buck,dsyang/buck,k21/buck,JoelMarcey/buck,SeleniumHQ/buck,robbertvanginkel/buck,vschs007/buck,robbertvanginkel/buck,brettwooldridge/buck,shs96c/buck,zhan-xiong/buck,zpao/buck,ilya-klyuchnikov/buck,ilya-klyuchnikov/buck,LegNeato/buck,Addepar/buck,marcinkwiatkowski/buck,shs96c/buck,marcinkwiatkowski/buck,LegNeato/buck,shs96c/buck,k21/buck,zhan-xiong/buck,zpao/buck,zpao/buck,shybovycha/buck,facebook/buck,marcinkwiatkowski/buck,ilya-klyuchnikov/buck,rmaz/buck,brettwooldridge/buck,kageiit/buck,zpao/buck,SeleniumHQ/buck,JoelMarcey/buck,clonetwin26/buck,SeleniumHQ/buck,dsyang/buck,romanoid/buck,SeleniumHQ/buck,k21/buck,brettwooldridge/buck,facebook/buck,shs96c/buck,romanoid/buck,k21/buck,Addepar/buck,Addepar/buck,brettwooldridge/buck,nguyentruongtho/buck,clonetwin26/buck,LegNeato/buck,ilya-klyuchnikov/buck,zpao/buck,marcinkwiatkowski/buck,robbertvanginkel/buck,clonetwin26/buck,marcinkwiatkowski/buck,brettwooldridge/buck,romanoid/buck,dsyang/buck,JoelMarcey/buck,romanoid/buck,kageiit/buck,SeleniumHQ/buck,clonetwin26/buck,SeleniumHQ/buck,kageiit/buck,shybovycha/buck,facebook/buck,robbertvanginkel/buck,romanoid/buck,brettwooldridge/buck,LegNeato/buck,zhan-xiong/buck,vschs007/buck,vschs007/buck,marcinkwiatkowski/buck,zhan-xiong/buck,nguyentruongtho/buck,vschs007/buck,clonetwin26/buck,k21/buck,rmaz/buck,marcinkwiatkowski/buck,ilya-klyuchnikov/buck,zpao/buck,dsyang/buck,dsyang/buck,vschs007/buck,JoelMarcey/buck,LegNeato/buck,vschs007/buck,ilya-klyuchnikov/buck,k21/buck,Addepar/buck,k21/buck,Addepar/buck,Addepar/buck,brettwooldridge/buck,Addepar/buck,rmaz/buck,rmaz/buck,zhan-xiong/buck,shs96c/buck,rmaz/buck,facebook/buck,dsyang/buck,SeleniumHQ/buck,vschs007/buck,kageiit/buck,LegNeato/buck,ilya-klyuchnikov/buck,zhan-xiong/buck,Addepar/buck,JoelMarcey/buck,zpao/buck,LegNeato/buck,clonetwin26/buck,shybovycha/buck,vschs007/buck,JoelMarcey/buck,nguyentruongtho/buck,LegNeato/buck,k21/buck,nguyentruongtho/buck,shs96c/buck,zhan-xiong/buck,romanoid/buck,brettwooldridge/buck,k21/buck,LegNeato/buck,rmaz/buck,SeleniumHQ/buck,facebook/buck,SeleniumHQ/buck,robbertvanginkel/buck,shs96c/buck,shybovycha/buck,brettwooldridge/buck,Addepar/buck,shybovycha/buck,clonetwin26/buck,dsyang/buck,dsyang/buck,romanoid/buck,shs96c/buck,rmaz/buck,robbertvanginkel/buck,dsyang/buck,JoelMarcey/buck,shybovycha/buck,robbertvanginkel/buck,vschs007/buck,zhan-xiong/buck,robbertvanginkel/buck,vschs007/buck,dsyang/buck,romanoid/buck,marcinkwiatkowski/buck,rmaz/buck,SeleniumHQ/buck,marcinkwiatkowski/buck,marcinkwiatkowski/buck,kageiit/buck,clonetwin26/buck,k21/buck,k21/buck,SeleniumHQ/buck,zhan-xiong/buck,clonetwin26/buck,robbertvanginkel/buck,robbertvanginkel/buck,shybovycha/buck,JoelMarcey/buck,robbertvanginkel/buck,nguyentruongtho/buck