Replace backticks with repr() or "%r"

From SF patch #852334.
diff --git a/Lib/idlelib/GrepDialog.py b/Lib/idlelib/GrepDialog.py
index 79fad31..ab136bc 100644
--- a/Lib/idlelib/GrepDialog.py
+++ b/Lib/idlelib/GrepDialog.py
@@ -77,7 +77,7 @@
         list.sort()
         self.close()
         pat = self.engine.getpat()
-        print "Searching %s in %s ..." % (`pat`, path)
+        print "Searching %r in %s ..." % (pat, path)
         hits = 0
         for fn in list:
             try: