Replace backticks with repr() or "%r"

From SF patch #852334.
diff --git a/Lib/test/test_asynchat.py b/Lib/test/test_asynchat.py
index 60017e0..e91c572 100644
--- a/Lib/test/test_asynchat.py
+++ b/Lib/test/test_asynchat.py
@@ -42,7 +42,7 @@
         self.buffer = self.buffer + data
 
     def found_terminator(self):
-        print "Received:", `self.buffer`
+        print "Received:", repr(self.buffer)
         self.buffer = ""
         self.close()