[issue15767] add ModuleNotFoundError

[Brett Cannon]

Brett Cannon added the comment:

TL;DR for Antoine: when using a fromlist, import failures from that list are silently ignored. Because ImportError is overloaded in terms of what it means (e.g. bag magic number, module not found) there needs to be a clean way to tell the import failed because the module wasn't found so other ImportError reasons can properly propagate.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue15767>
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