Fix up the build_file_mask_string test.

- Fix up the build_file_mask_string test by mocking out the __init__() method of the PresentationMediaItem class
    - Change the way of calling the parent __init__() method to something slightly better (though it has nothing to do with the test)

openlp/plugins/presentations/lib/mediaitem.py

@@ -59,7 +59,7 @@ class PresentationMediaItem(MediaManagerItem):
         self.controllers = controllers
         self.icon_path = u'presentations/presentation'
         self.Automatic = u''
-        MediaManagerItem.__init__(self, parent, plugin)
+        super(PresentationMediaItem, self).__init__(parent, plugin)
         self.message_listener = MessageListener(self)
         self.has_search = True
         self.single_service_item = False

tests/functional/openlp_plugins/presentations/test_mediaitem.py

@@ -26,9 +26,9 @@ class TestMediaItem(TestCase):
         Registry().register(u'service_manager', MagicMock())
         Registry().register(u'main_window', MagicMock())
 
-        with patch('openlp.core.lib.mediamanageritem.MediaManagerItem.__init__'),  \
-                patch('openlp.core.lib.mediamanageritem.ListWidgetWithDnD'):
-            self.media_item = PresentationMediaItem(MagicMock(), MagicMock(), MagicMock(), MagicMock())
+        with patch('openlp.plugins.presentations.lib.mediaitem.PresentationMediaItem.__init__') as mocked_init:
+            mocked_init.return_value = None
+            self.media_item = PresentationMediaItem(MagicMock(), MagicMock, MagicMock(), MagicMock())
 
         self.application = QtGui.QApplication.instance()