[issue3623] _json: fix raise_errmsg(), py_encode_basestring_ascii() and linecol()

[Amaury Forgeot d'Arc]

Changes by Amaury Forgeot d'Arc <amauryfa at gmail.com>:


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keywords: +needs review

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue3623>
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