Replace backticks with repr() or "%r"

From SF patch #852334.
diff --git a/Doc/lib/caseless.py b/Doc/lib/caseless.py
index 107fed6..b128219 100755
--- a/Doc/lib/caseless.py
+++ b/Doc/lib/caseless.py
@@ -47,10 +47,10 @@
         print "not ok: no conflict between -h and -H"
     
     parser.add_option("-f", "--file", dest="file")
-    #print `parser.get_option("-f")`
-    #print `parser.get_option("-F")`
-    #print `parser.get_option("--file")`
-    #print `parser.get_option("--fIlE")`
+    #print repr(parser.get_option("-f"))
+    #print repr(parser.get_option("-F"))
+    #print repr(parser.get_option("--file"))
+    #print repr(parser.get_option("--fIlE"))
     (options, args) = parser.parse_args(["--FiLe", "foo"])
     assert options.file == "foo", options.file
     print "ok: case insensitive long options work"