Replace backticks with repr() or "%r"

From SF patch #852334.
diff --git a/Demo/newmetaclasses/Enum.py b/Demo/newmetaclasses/Enum.py
index 8a00b59..5d490a9 100644
--- a/Demo/newmetaclasses/Enum.py
+++ b/Demo/newmetaclasses/Enum.py
@@ -97,7 +97,7 @@
 
     print Color.red
 
-    print `Color.red`
+    print repr(Color.red)
     print Color.red == Color.red
     print Color.red == Color.blue
     print Color.red == 1
@@ -139,7 +139,7 @@
 
     print Color.red
 
-    print `Color.red`
+    print repr(Color.red)
     print Color.red == Color.red
     print Color.red == Color.blue
     print Color.red == 1