Replace backticks with repr() or "%r"

From SF patch #852334.
diff --git a/Lib/idlelib/RemoteDebugger.py b/Lib/idlelib/RemoteDebugger.py
index bdcef51..74085c3 100644
--- a/Lib/idlelib/RemoteDebugger.py
+++ b/Lib/idlelib/RemoteDebugger.py
@@ -94,7 +94,7 @@
         self.idb.set_return(frame)
 
     def get_stack(self, fid, tbid):
-        ##print >>sys.__stderr__, "get_stack(%s, %s)" % (`fid`, `tbid`)
+        ##print >>sys.__stderr__, "get_stack(%r, %r)" % (fid, tbid)
         frame = frametable[fid]
         if tbid is None:
             tb = None
@@ -295,7 +295,7 @@
     def call(self, methodname, *args, **kwargs):
         ##print "**IdbProxy.call %s %s %s" % (methodname, args, kwargs)
         value = self.conn.remotecall(self.oid, methodname, args, kwargs)
-        ##print "**IdbProxy.call %s returns %s" % (methodname, `value`)
+        ##print "**IdbProxy.call %s returns %r" % (methodname, value)
         return value
 
     def run(self, cmd, locals):