# File lib/net/http/persistent.rb, line 591
  def error_message connection
    requests = Thread.current[@request_key][connection.object_id] - 1 # fixup
    last_use = Thread.current[@timeout_key][connection.object_id]

    age = Time.now - last_use

    "after #{requests} requests on #{connection.object_id}, " \
      "last used #{age} seconds ago"
  end