[pitivi] Use named placeholder syntax in translatable string

[Claude Paroz <claudep src gnome org>]

commit 2165b5770c6a836a4921b85da4ffeb32f01d8d27
Author: Claude Paroz <claude 2xlibre net>
Date:   Thu May 21 18:44:33 2009 +0200

    Use named placeholder syntax in translatable string
---
 pitivi/ui/pluginmanagerdialog.py |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pitivi/ui/pluginmanagerdialog.py b/pitivi/ui/pluginmanagerdialog.py
index 601f7c7..bf10cc2 100644
--- a/pitivi/ui/pluginmanagerdialog.py
+++ b/pitivi/ui/pluginmanagerdialog.py
@@ -321,8 +321,8 @@ class PluginManagerDialog(object):
                     message_format = _("Update the existent plugin?"))
 
                 dialog.format_secondary_text(
-                    _("This plugin is already installed in your system.\nIf you agree, version %s will be replaced with version %s")\
-                    %(e.old_plugin.version, e.new_plugin.version))
+                    _("This plugin is already installed in your system.\nIf you agree, version %(v1)s will be replaced with version %(v2)s")\
+                    %{'v1': e.old_plugin.version, 'v2': e.new_plugin.version})
 
                 dialog.set_title(_("Duplicate plugin found"))
                 try: