[issue9912] Fail when vsvarsall.bat produces stderr

[Mark Lawrence]

Mark Lawrence added the comment:

The patch is two extra lines that look fine to me, can somebody do a commit review please?

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components:  -Distutils2
nosy: +BreamoreBoy, dstufft
versions: +Python 3.4, Python 3.5 -3rd party, Python 3.2

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<http://bugs.python.org/issue9912>
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