Replace backticks with repr() or "%r"

From SF patch #852334.
diff --git a/Lib/distutils/fancy_getopt.py b/Lib/distutils/fancy_getopt.py
index a4a4e79..512bc9b 100644
--- a/Lib/distutils/fancy_getopt.py
+++ b/Lib/distutils/fancy_getopt.py
@@ -162,7 +162,7 @@
             else:
                 # the option table is part of the code, so simply
                 # assert that it is correct
-                assert "invalid option tuple: %s" % `option`
+                assert "invalid option tuple: %r" % (option,)
 
             # Type- and value-check the option names
             if type(long) is not StringType or len(long) < 2: