pr.rb in circleci-bundle-update-pr-1.16.1

- old
+ new

@@ -36,10 +36,10 @@
           add_assignees(pull_request[:number], assignees) if assignees
           request_review(pull_request[:number], reviewers) if reviewers
         end
 
         BRANCH_PREFIX = ENV['BRANCH_PREFIX'] || 'bundle-update-'.freeze
-        TITLE_PREFIX = 'bundle update at '.freeze
+        TITLE_PREFIX = ENV['TITLE_PREFIX'] || 'bundle update at '.freeze
 
         def self.raise_if_env_unvalid!
           raise "$CIRCLE_PROJECT_USERNAME isn't set" unless ENV['CIRCLE_PROJECT_USERNAME']
           raise "$CIRCLE_PROJECT_REPONAME isn't set" unless ENV['CIRCLE_PROJECT_REPONAME']
           raise "$GITHUB_ACCESS_TOKEN isn't set" unless ENV['GITHUB_ACCESS_TOKEN']