Critic review: https://critic.hoppipolla.co.uk/r/490

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I tested this in my app which used FancyURLOpener().open(), and returned a urllib.response.addinfourl instance. using Python 3.3 (Python 2.7 and 3.2 were unaffected), before the patch, the parser returned an empty html document. Afterwards it returned the expected content. Thanks @SimonSapin

As I said on IRC to @SimonSapin: Can we change this to just pass a firstChunk into HTMLUnicodeInputStream and HTMLBinaryInputStream, so we can work around all 20007 issues all at one? It's ugly, but it stops endless isinstance checks for this.