Index: Lib/distutils/msvc9compiler.py
===================================================================
--- Lib/distutils/msvc9compiler.py	(revision 84963)
+++ Lib/distutils/msvc9compiler.py	(working copy)
@@ -267,6 +267,8 @@
     stdout, stderr = popen.communicate()
     if popen.wait() != 0:
         raise DistutilsPlatformError(stderr.decode("mbcs"))
+    if stderr:
+        log.warn("vcvarsall.bat created stderr: %s", stderr.decode("mbcs")
 
     stdout = stdout.decode("mbcs")
     for line in stdout.split("\n"):