[docs] [issue20923] Explain ConfigParser 'valid section name' and .SECTCRE

[Terry J. Reedy]

Changes by Terry J. Reedy <tjreedy at udel.edu>:


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title: ConfigParser should nested [] in section names. -> Explain ConfigParser 'valid section name' and .SECTCRE

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue20923>
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