Prevent memory leak on error.

Reported by Klocwork #36
diff --git a/Modules/cPickle.c b/Modules/cPickle.c
index 9d979de..24c98cc 100644
--- a/Modules/cPickle.c
+++ b/Modules/cPickle.c
@@ -3401,11 +3401,11 @@
 	/********************************************/
 
 	str = PyString_DecodeEscape(p, len, NULL, 0, NULL);
+	free(s);
 	if (str) {
 		PDATA_PUSH(self->stack, str, -1);
 		res = 0;
 	}
-	free(s);
 	return res;
 
   insecure: