Ensure there's always an opened GDK display present

Sometimes it happens that there's no GDK display present and this
leads to a traceback when a keyCombo() is sent. It's not entirely
sure if this is a bug in dogtail or if we should open the display
explicitly ourselves. We can remove this piece of code in the future
if we find out that this should rather get fixed in dogtail.

anabot/runtime/run_test.py

@@ -19,6 +19,28 @@ def run_test(file_path, appname="anaconda", children_required=0):
     that this file is already processed by anabot preprocessor.
     See anabot.preprocessor package.
     """
+    from gi import require_version
+    require_version('Gdk', '3.0')
+    from gi.repository import Gdk # pylint: disable=no-name-in-module
+
+    # Workaround for a situation when a default display is missing for some reason.
+    # It is not clear at this point whether this really is a workaround and it should be
+    # fixed (potentially) in dogtail.
+    if Gdk.Display.get_default() is None:
+        import os
+        logger.debug("Default GDK display not found! Opening the display explicitly.")
+        if "WAYLAND_DISPLAY" in os.environ.keys():
+            display_name = os.environ["WAYLAND_DISPLAY"]
+        elif "DISPLAY" in os.environ.keys():
+            display_name = os.environ["DISPLAY"]
+        else:
+            logger.error("Can't find a display name to open explicitly, Anabot run may fail!")
+            # Let's assume Anaconda running on Wayland, as this is likely the only problematic
+            # configuration anyway.
+            display_name = "wl-sysinstall-0"
+        Gdk.Display.open(display_name)
+        logger.debug(f"Explicitly opened display: '{Gdk.Display.get_default().get_name()}'")
+
     import dogtail.config # pylint: disable=import-error
     dogtail.config.config.checkForA11y = False
     dogtail.config.config.typingDelay = 0.2