'error' 事件
'error' 事件可以随时由 Readable 的实现触发。
通常，如果底层流由于底层内部故障而无法生成数据，或者当流实现尝试推送无效数据块时，可能会发生这种情况。
监听器回调将传入单个 Error 对象。
The 'error' event may be emitted by a Readable implementation at any time.
Typically, this may occur if the underlying stream is unable to generate data
due to an underlying internal failure, or when a stream implementation attempts
to push an invalid chunk of data.
The listener callback will be passed a single Error object.