def on_complete(env)
      if env[:body].error?
        @logger.warn env[:raw_body] if VkontakteApi.log_errors?
      else
        @logger.debug env[:raw_body] if VkontakteApi.log_responses?
      end
    end
def on_complete(env)
      if env[:body].error?
        @logger.warn env[:raw_body] if VkontakteApi.log_errors?
      else
        @logger.debug env[:raw_body] if VkontakteApi.log_responses?
      end
    end
Logs the response (successful or not) if needed.
 @param [Hash] env Response data.