[issue20422] Signature.from_builtin should raise a ValueError when no signature can be provided

[Yury Selivanov]

Yury Selivanov added the comment:

A patch is attached, please review.

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keywords: +needs review, patch
stage:  -> patch review
Added file: http://bugs.python.org/file33784/from_builtin_errors_01.patch

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<http://bugs.python.org/issue20422>
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