Print stacktrace on Qt warnings.

qutebrowser/utils/log.py

@@ -26,6 +26,7 @@ import logging
 import contextlib
 import collections
 import faulthandler
+import traceback
 
 from PyQt5.QtCore import (QtDebugMsg, QtWarningMsg, QtCriticalMsg, QtFatalMsg,
                           qInstallMessageHandler)
@@ -294,8 +295,16 @@ def qt_message_handler(msg_type, context, msg):
         msg += ("\n\nOn Archlinux, this should fix the problem:\n"
                 "    pacman -S libxkbcommon-x11")
         faulthandler.disable()
+    try:
+        frame = sys._getframe(1)
+    except (AttributeError, ValueError):
+        # sys._getframe might not exist in some Python implementations.
+        # It could raise ValueError if the stack is less than one level deep -
+        # this SHOULD never happen, but we're better safe than sorry here.
+        frame = None
+    stack = ''.join(traceback.format_stack(f=frame))
     record = qt.makeRecord(name, level, context.file, context.line, msg, None,
-                           None, func)
+                           None, func, sinfo=stack)
     qt.handle(record)