Don't return unfound VS version, raise instead
Don't return unfound VS version, raise instead

This fallback behaviour may have worked at some point, but doesn't
any more, so simply error out with a clear message rather than trying
to continue.

R=timurrrr@chromium.org
BUG=https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/O_OGfq2nhSw

Review URL: https://codereview.chromium.org/595543003

git-svn-id: e7e1075985beda50ea81ac4472467b4f6e91fc78@1978 78cadc50-ecff-11dd-a971-7dbc132099af

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