log: Set line number to -1 if it's None for Qt messages

If lineno is set to None in the LogRecord, pytest's logging formatting fails:

    tests/unit/utils/test_log.py:418: in test_empty_message
        log.qt_message_handler(QtCore.QtDebugMsg, self.Context(), "")
    qutebrowser/utils/log.py:508: in qt_message_handler
        qt.handle(record)
    /usr/lib/python3.8/logging/__init__.py:1587: in handle
        self.callHandlers(record)
    /usr/lib/python3.8/logging/__init__.py:1649: in callHandlers
        hdlr.handle(record)
    /usr/lib/python3.8/logging/__init__.py:950: in handle
        self.emit(record)
    ../../pytest/src/_pytest/logging.py:326: in emit
        super().emit(record)
    /usr/lib/python3.8/logging/__init__.py:1089: in emit
        self.handleError(record)
    /usr/lib/python3.8/logging/__init__.py:1081: in emit
        msg = self.format(record)
    /usr/lib/python3.8/logging/__init__.py:925: in format
        return fmt.format(record)
    ../../pytest/src/_pytest/logging.py:89: in format
        return super().format(record)
    /usr/lib/python3.8/logging/__init__.py:667: in format
        s = self.formatMessage(record)
    /usr/lib/python3.8/logging/__init__.py:636: in formatMessage
        return self._style.format(record)
    ../../pytest/src/_pytest/logging.py:185: in format
        return self._fmt % record.__dict__
    E   TypeError: %d format: a number is required, not NoneType

According to typeshed, lineno should never be None:
https://github.com/python/typeshed/blob/028f0d52931fe1f96bb25d066186961159c1f801/stdlib/2and3/logging/__init__.pyi#L386

Thus, this is our fault, not pytest's. However, before pytest 6.0.0, pytest did
not surface logging errors:

pytest-dev/pytest#7231
pytest-dev/pytest@b13fcb2

Thus, we never noticed something was going wrong here.

(cherry picked from commit e206d34)

Make mypy happy

It doesn't know about QMessageLogContext.lineno being Optional[int] rather than
int.

(cherry picked from commit 4136c84)

Author: The-Compiler

qutebrowser/utils/log.py

@@ -477,6 +477,11 @@ def qt_message_handler(msg_type: QtCore.QtMsgType,
     else:
         level = qt_to_logging[msg_type]
 
+    if context.line is None:
+        lineno = -1  # type: ignore[unreachable]
+    else:
+        lineno = context.line
+
     if context.function is None:
         func = 'none'  # type: ignore[unreachable]
     elif ':' in context.function:
@@ -503,7 +508,7 @@ def qt_message_handler(msg_type: QtCore.QtMsgType,
     else:
         stack = None
 
-    record = qt.makeRecord(name, level, context.file, context.line, msg, (),
+    record = qt.makeRecord(name, level, context.file, lineno, msg, (),
                            None, func, sinfo=stack)
     qt.handle(record)