Don't return unfound VS version, raise instead

pylib/gyp/MSVSVersion.py

Index: pylib/gyp/MSVSVersion.py
diff --git a/pylib/gyp/MSVSVersion.py b/pylib/gyp/MSVSVersion.py
index bcd6122f2dfc9ff457242833c84a6fb1a3339e99..8b01f7a3fea58032ebba2b5075e5d3eff35c47ac 100644
--- a/pylib/gyp/MSVSVersion.py
+++ b/pylib/gyp/MSVSVersion.py
@@ -401,9 +401,5 @@ def SelectVisualStudioVersion(version='auto'):
   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]