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: http://gyp.googlecode.com/svn/trunk@1978 78cadc50-ecff-11dd-a971-7dbc132099af
diff --git a/pylib/gyp/MSVSVersion.py b/pylib/gyp/MSVSVersion.py
index bcd6122..8b01f7a 100644
--- a/pylib/gyp/MSVSVersion.py
+++ b/pylib/gyp/MSVSVersion.py
@@ -401,9 +401,5 @@
   version = str(version)
   versions = _DetectVisualStudioVersions(version_map[version], 'e' in version)
   if not versions:
-    if version == 'auto':
-      # Default to 2005 if we couldn't find anything
-      return _CreateVersion('2005', None)
-    else:
-      return _CreateVersion(version, None)
+    raise ValueError('Could not locate Visual Studio installation.')
   return versions[0]