[issue40372] doctest example programs should exit 1 if any test fails

[Rémi Lapeyre]

Change by Rémi Lapeyre <remi.lapeyre at henki.fr>:


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nosy: +remi.lapeyre, tim.peters
versions:  -Python 2.7, Python 3.5, Python 3.6

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40372>
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