[issue13274] heapq pure python version uses islice without guarding for negative counts

[Ronny Pfannschmidt]

New submission from Ronny Pfannschmidt <ronny.pfannschmidt at gmail.com>:

the problem manifests when calling with negative counts

when the c versions are used, a empty list is returned,
however if the pure python version is called islice errors out

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components: Library (Lib)
messages: 146483
nosy: Ronny.Pfannschmidt
priority: normal
severity: normal
status: open
title: heapq pure python version uses islice without guarding for negative counts
type: behavior
versions: Python 2.6, Python 2.7, Python 3.1, Python 3.2, Python 3.3, Python 3.4

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue13274>
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