Add missing newline to error message
Add missing newline to error message

Summary:
This pull request adds a missing newline to the error message that's shown when the error summary is truncated.
Closes https://github.com/facebook/flow/pull/2511

Differential Revision: D3906392

Pulled By: mroch

fbshipit-source-id: fd113b371f470fa48986691b623e497c3e6dc545

jgrund/flow,claudiopro/flow,ForbesLindesay/flow,claudiopro/flow,JonathanUsername/flow,jamesgpearce/flow,samwgoldman/flow,MichaelDeBoey/flow,facebook/flow,gabelevi/flow,AgentME/flow,gabro/flow,samwgoldman/flow,popham/flow,gabro/flow,fletcherw/flow,nmote/flow,JonathanUsername/flow,chenglou/flow,AprilArcus/flow,gabro/flow,nmote/flow,gabelevi/flow,ylu1317/flow,popham/flow,jgrund/flow,fletcherw/flow,ylu1317/flow,facebook/flow,TiddoLangerak/flow,gabro/flow,AgentME/flow,facebook/flow,jamesgpearce/flow,AgentME/flow,MichaelDeBoey/flow,chenglou/flow,jgrund/flow,claudiopro/flow,jamesgpearce/flow,nmote/flow,fletcherw/flow,facebook/flow,popham/flow,gabelevi/flow,mroch/flow,nmote/flow,JonathanUsername/flow,ForbesLindesay/flow,TiddoLangerak/flow,samwgoldman/flow,chenglou/flow,mroch/flow,ylu1317/flow,popham/flow,AprilArcus/flow,mroch/flow,jamesgpearce/flow,claudiopro/flow,AgentME/flow,gabelevi/flow,nmote/flow,jamesgpearce/flow,MichaelDeBoey/flow,claudiopro/flow,ForbesLindesay/flow,jgrund/flow,jgrund/flow,popham/flow,chenglou/flow,ForbesLindesay/flow,gabelevi/flow,chenglou/flow,MichaelDeBoey/flow,gabro/flow,samwgoldman/flow,popham/flow,TiddoLangerak/flow,facebook/flow,ForbesLindesay/flow,nmote/flow,gabelevi/flow,JonathanUsername/flow,JonathanUsername/flow,MichaelDeBoey/flow,gabro/flow,AprilArcus/flow,jgrund/flow,TiddoLangerak/flow,mroch/flow,chenglou/flow,AprilArcus/flow,jamesgpearce/flow,JonathanUsername/flow,AprilArcus/flow,ylu1317/flow,fletcherw/flow,mroch/flow,mroch/flow,AgentME/flow,mroch/flow,AprilArcus/flow,ForbesLindesay/flow,facebook/flow,ylu1317/flow,JonathanUsername/flow,TiddoLangerak/flow,samwgoldman/flow,samwgoldman/flow,gabelevi/flow,samwgoldman/flow,popham/flow,fletcherw/flow,facebook/flow,nmote/flow,jamesgpearce/flow,fletcherw/flow