Update imports, copyright notices.

joy/vui/stack_viewer.py

@@ -1,5 +1,24 @@
+# -*- coding: utf-8 -*-
+#
+#    Copyright © 2019 Simon Forman
+#
+#    This file is part of Thun
+#
+#    Thun is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License as published by
+#    the Free Software Foundation, either version 3 of the License, or
+#    (at your option) any later version.
+#
+#    Thun is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with Thun.  If not see <http://www.gnu.org/licenses/>.
+#
 from joy.utils.stack import expression_to_string, iter_stack
-import core, text_viewer
+from joy.vui import core, text_viewer
 
 
 MAX_WIDTH = 64