Raise exception when a stylesheet is unparsable.

qutebrowser/utils/log.py

@@ -133,6 +133,11 @@ sessions = logging.getLogger('sessions')
 ram_handler = None
 
 
+class CriticalQtWarning(Exception):
+
+    """Exception raised when there's a critical Qt warning."""
+
+
 def init_log(args):
     """Init loggers based on the argparse namespace passed."""
     level = 'VDEBUG' if args.debug else args.loglevel.upper()
@@ -301,7 +306,17 @@ def qt_message_handler(msg_type, context, msg):
                 'with: -9805',  # noqa
         ]
 
-    if any(msg.strip().startswith(pattern) for pattern in suppressed_msgs):
+    # Messages which will trigger an exception immediately
+    critical_msgs = [
+        'Could not parse stylesheet of object',
+    ]
+
+    if any(msg.strip().startswith(pattern) for pattern in critical_msgs):
+        # For some reason, the stack gets lost when raising here...
+        logger = logging.getLogger('misc')
+        logger.error("Got critical Qt warning!", stack_info=True)
+        raise CriticalQtWarning(msg)
+    elif any(msg.strip().startswith(pattern) for pattern in suppressed_msgs):
         level = logging.DEBUG
     else:
         level = qt_to_logging[msg_type]