Fix typo in abstract.c which caused __rpow__ to not be invoked.
Added related testcase.
Closes SF bug #643260.
diff --git a/Lib/test/test_pow.py b/Lib/test/test_pow.py
index 2b3465c..e88a63d 100644
--- a/Lib/test/test_pow.py
+++ b/Lib/test/test_pow.py
@@ -118,3 +118,8 @@
                 o = pow(long(i),j) % k
                 n = pow(long(i),j,k)
                 if o != n: print 'Integer mismatch:', i,j,k
+
+class TestRpow:
+    def __rpow__(self, other):
+        return None
+None ** TestRpow()      # Won't fail when __rpow__ invoked.  SF bug #643260.