pr.rb in circleci-bundle-update-pr-1.3.5

- old
+ new

@@ -23,10 +23,12 @@
           add_comment_of_compare_linker(repo_full_name, pull_request[:number])
         end
 
         def self.need?(git_branches)
           return false unless git_branches.include?(ENV['CIRCLE_BRANCH'])
-          system("bundle update")
+          unless system("bundle update")
+            raise "Unable to execute `bundle update`"
+          end
           `git status -sb 2> /dev/null`.include?("Gemfile.lock")
         end
         private_class_method :need?
 
         def self.create_branch(git_username, git_email, branch)