[docs] [issue13899] re pattern r"[\A]" should work like "A" but matches nothing. Ditto B and Z.

[Jesús Cea Avión]

Changes by Jesús Cea Avión <jcea at jcea.es>:


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nosy: +jcea

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue13899>
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