Use :text for the last_error field

generators/delayed_job/templates/migration.rb

@@ -4,7 +4,7 @@ def self.up
       table.integer  :priority, :default => 0      # Allows some jobs to jump to the front of the queue
       table.integer  :attempts, :default => 0      # Provides for retries, but still fail eventually.
       table.text     :handler                      # YAML-encoded string of the object that will do work
-      table.string   :last_error                   # reason for last failure (See Note below)
+      table.text     :last_error                   # reason for last failure (See Note below)
       table.datetime :run_at                       # When to run. Could be Time.now for immediately, or sometime in the future.
       table.datetime :locked_at                    # Set when a client is working on this object
       table.datetime :failed_at                    # Set when all retries have failed (actually, by default, the record is deleted instead)