unbreak the CI which doesn't have an X11 display

tests/unittests/unit/gtk_common/keymap_test.py

@@ -4,15 +4,18 @@
 # Xpra is released under the terms of the GNU GPL v2, or, at your option, any
 # later version. See the file COPYING for details.
 
+import os
 import unittest
 
+from xpra.os_util import POSIX
 from xpra.gtk.keymap import get_gtk_keymap
 
 
 class TestKeymap(unittest.TestCase):
 
     def test_get_gtk_keymap(self):
-        assert get_gtk_keymap()
+        if not POSIX or os.environ.get("DISPLAY"):
+            assert get_gtk_keymap()
 
 
 def main():