Convert raise statements in Tools/.
diff --git a/Tools/freeze/winmakemakefile.py b/Tools/freeze/winmakemakefile.py
index e473fed..7d198c1 100644
--- a/Tools/freeze/winmakemakefile.py
+++ b/Tools/freeze/winmakemakefile.py
@@ -39,7 +39,7 @@
     try:
         return subsystem_details[subsystem][:2]
     except KeyError:
-        raise ValueError, "The subsystem %s is not known" % subsystem
+        raise ValueError("The subsystem %s is not known" % subsystem)
 
 
 def makemakefile(outfp, vars, files, target):