sidebar: Give the New Playlist entry the "card" style class

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

emmental/sidebar/playlist.py

@@ -58,6 +58,7 @@ class Section(section.Section):
         self._entry.connect("activate", self.__add_new_playlist)
         self._entry.connect("changed", self.__entry_changed)
         self._entry.connect("icon-release", self.__entry_icon_release)
+        self._entry.add_css_class("card")
 
     def __add_new_playlist(self, entry: Gtk.Entry) -> None:
         if self.table.create(entry.get_text()) is not None:

tests/sidebar/test_playlist.py

@@ -67,6 +67,7 @@ class TestPlaylists(tests.util.TestCase):
                          Gtk.EntryIconPosition.PRIMARY), "list-add")
         self.assertIsNone(self.playlists._entry.get_icon_name(
                           Gtk.EntryIconPosition.SECONDARY))
+        self.assertTrue(self.playlists._entry.has_css_class("card"))
 
         with unittest.mock.patch.object(self.playlists.extra_widget,
                                         "popdown") as mock_popdown: