ci: Also check GTK4 when testing PyGObject availability

Author: QuLogic

.github/workflows/tests.yml

@@ -219,10 +219,14 @@ jobs:
           # libraries cannot be loaded at runtime, so an actual import is a
           # better check).
           # PyGObject, pycairo, and cariocffi do not install on OSX 10.12.
-           python -m pip install --upgrade pycairo 'cairocffi>=0.8' PyGObject &&
-             python -c 'import gi; gi.require_version("Gtk", "3.0"); from gi.repository import Gtk' &&
-             echo 'PyGObject is available' ||
-             echo 'PyGObject is not available'
+          python -m pip install --upgrade pycairo 'cairocffi>=0.8' PyGObject &&
+            (
+              python -c 'import gi; gi.require_version("Gtk", "4.0"); from gi.repository import Gtk' &&
+              echo 'PyGObject 4 is available' || echo 'PyGObject 4 is not available'
+            ) && (
+              python -c 'import gi; gi.require_version("Gtk", "3.0"); from gi.repository import Gtk' &&
+              echo 'PyGObject 3 is available' || echo 'PyGObject 3 is not available'
+            )
 
           # There are no functioning wheels available for OSX 10.12 (as of
           # Sept 2020) for either pyqt5 (there are only wheels for 10.13+) or