use default error message when no message is provided. don't fetch message key

Author: ABaldwinHunter

lib/cc/services/github_pull_requests.rb

@@ -91,7 +91,7 @@ def presenter
   def update_status_error
     update_status(
       "error",
-      message
+      @payload["message"] || DEFAULT_ERROR
     )
   end
 
@@ -197,10 +197,6 @@ def commit_sha
     @payload.fetch("commit_sha")
   end
 
-  def message
-    @payload.fetch("message")
-  end
-
   def number
     @payload.fetch("number")
   end