Added conditional for gui tests, which depends on graphical environment

tests/test_message.py

@@ -1,10 +1,5 @@
 from unittest import TestCase
-try:
+import os
-    import tkinter as tk
-    from tkinter import ttk
-except ImportError:
-    import Tkinter as tk
-    import ttk
 
 try:
     from unittest import mock
@@ -13,6 +8,14 @@ except ImportError:
 
 from fs_uae_wrapper import message
 
+if os.environ.get('DISPLAY'):
+    try:
+        import tkinter as tk
+        from tkinter import ttk
+    except ImportError:
+        import Tkinter as tk
+        import ttk
+
 
 class TestMessage(TestCase):
 
@@ -44,15 +47,16 @@ class TestMessage(TestCase):
         msg._process.join.assert_called_once()
 
 
-class TestSpawn(TestCase):
+if os.environ.get('DISPLAY'):
+    # Tkinter needs graphic environment for the widgets
+    class TestSpawn(TestCase):
 
         @mock.patch('fs_uae_wrapper.message.MessageGui.__call__')
         def test_spawn(self, call):
             self.assertIsNone(message._spawn(''))
             call.assert_called_once()
 
-
+    class TestMessageGui(TestCase):
-class TestMessageGui(TestCase):
 
         def test_gui(self):
             msg = message.MessageGui(msg='display that')