We can use QtCore in fix_harfbuzz so use logging

qutebrowser/qutebrowser.py

@@ -58,12 +58,14 @@ def main():
     """Main entry point for qutebrowser."""
     earlyinit.init_faulthandler()
     args = _parse_args()
-    earlyinit.fix_harfbuzz(args)
     earlyinit.check_pyqt_core()
-    earlyinit.check_pyqt_webkit()
-    # We do these imports late as we need to do the early init first.
+    # We do this import late as we need to do the version checking first.
+    # Note we may not import webkit stuff yet as fix_harfbuzz didn't run.
     import qutebrowser.utils.log as log
-    from qutebrowser.app import Application
     log.init_log(args)
+    earlyinit.fix_harfbuzz(args)
+    earlyinit.check_pyqt_webkit()
+    # We do this import late as we need to fix harfbuzz first.
+    from qutebrowser.app import Application
     app = Application(args)
     return app.exec_()

qutebrowser/utils/earlyinit.py

@@ -24,7 +24,6 @@ import faulthandler
 import textwrap
 import traceback
 import signal
-import warnings
 
 
 # Now we initialize the faulthandler as early as possible, so we theoretically
@@ -61,11 +60,15 @@ def fix_harfbuzz(args):
     This fixes crashes on various sites.
     See https://bugreports.qt-project.org/browse/QTBUG-36099
 
+    IMPORTANT: This needs to be done before QWidgets is imported in any way!
+
     Args:
         args: The argparse namespace.
     """
-    if 'PyQt5' in sys.modules:
-        warnings.warn("Harfbuzz fix attempted but PyQt5 is already imported!")
+    from qutebrowser.utils.log import init as logger
+    if 'PyQt5.QtWidgets' in sys.modules:
+        logger.warning("Harfbuzz fix attempted but QtWidgets is already "
+                       "imported!")
     if sys.platform.startswith('linux') and args.harfbuzz == 'auto':
         os.environ['QT_HARFBUZZ'] = 'old'
     elif args.harfbuzz == 'old':