# Buggy code
def tabSizeHint(self, index: int):
    """Override tabSizeHint to customize qb's tab size.

    https://wiki.python.org/moin/PyQt/Customising%20tab%20bars

    Args:
        index: The index of the tab.

    Return:
        A QSize.
    """
    minimum_size = self.minimumTabSizeHint(index)
    height = minimum_size.height()
    if self.vertical:
        confwidth = str(config.val.tabs.width)
        if confwidth.endswith("%"):
            main_window = objreg.get("main-window", scope="window", window=self._win_id)
            perc = int(confwidth.rstrip("%"))
            width = main_window.width() * perc / 100
        else:
            width = int(confwidth)
        size = QSize(max(minimum_size.width(), width), height)
    elif self.count() == 0:
        # This happens on startup on macOS.
        # We return it directly rather than setting `size' because we don't
        # want to ensure it's valid in this special case.
        return QSize()
    else:
        if config.val.tabs.pinned.shrink:
            pinned = self._tab_pinned(index)
            pinned_count, pinned_width = self._pinned_statistics()
        else:
            pinned = False
            pinned_count, pinned_width = 0, 0
        no_pinned_count = self.count() - pinned_count
        no_pinned_width = self.width() - pinned_width

        if pinned:
            # Give pinned tabs the minimum size they need to display their
            # titles, let Qt handle scaling it down if we get too small.
            width = self.minimumTabSizeHint(index, ellipsis=False).width()
        else:
            width = no_pinned_width / no_pinned_count

        # If no_pinned_width is not divisible by no_pinned_count, add a
        # pixel to some tabs so that there is no ugly leftover space.
        if no_pinned_count > 0 and index < no_pinned_width % no_pinned_count:
            width += 1

        # If we don't have enough space, we return the minimum size so we
        # get scroll buttons as soon as needed.
        width = max(width, minimum_size.width())

        size = QSize(width, height)
    qtutils.ensure_valid(size)
    return size


# Traceback (ValueError)
16:39:44 DEBUG    init       app:_init_modules:468 Initializing websettings...
16:39:45 ERROR    misc       crashsignal:exception_hook:216 Uncaught exception
Traceback (most recent call last):
File "/bin/qutebrowser", line 11, in <module>
load_entry_point('qutebrowser==1.1.1', 'gui_scripts', 'qutebrowser')()
File "/usr/lib/python3.6/site-packages/qutebrowser/qutebrowser.py", line 188, in main
return app.run(args)
File "/usr/lib/python3.6/site-packages/qutebrowser/app.py", line 137, in run
init(args, crash_handler)
File "/usr/lib/python3.6/site-packages/qutebrowser/app.py", line 163, in init
_init_modules(args, crash_handler)
File "/usr/lib/python3.6/site-packages/qutebrowser/app.py", line 469, in _init_modules
websettings.init(args)
File "/usr/lib/python3.6/site-packages/qutebrowser/config/websettings.py", line 215, in init
webenginesettings.init(args)
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/webenginesettings.py", line 297, in init
websettings.init_mappings(MAPPINGS)
File "/usr/lib/python3.6/site-packages/qutebrowser/config/websettings.py", line 198, in init_mappings
mapping.set(value)
File "/usr/lib/python3.6/site-packages/qutebrowser/config/websettings.py", line 72, in set
self._set(value, settings=settings)
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/webenginesettings.py", line 154, in _set
filenames = [self._find_installed(code) for code in value]
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/webenginesettings.py", line 154, in <listcomp>
filenames = [self._find_installed(code) for code in value]
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/webenginesettings.py", line 143, in _find_installed
local_filename = spell.local_filename(code)
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/spell.py", line 64, in local_filename
all_installed = local_files(code)
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/spell.py", line 51, in local_files
for matching_dict in sorted(matching_dicts, key=version, reverse=True):
File "/usr/lib/python3.6/site-packages/qutebrowser/browser/webengine/spell.py", line 36, in version
.format(filename))
ValueError: the given dictionary file name is malformed: /usr/share/qt/qtwebengine_dictionaries/en-US.bdic

# Fixed code
def tabSizeHint(self, index: int):
    """Override tabSizeHint to customize qb's tab size.

    https://wiki.python.org/moin/PyQt/Customising%20tab%20bars

    Args:
        index: The index of the tab.

    Return:
        A QSize.
    """
    if self.count() == 0:
        # This happens on startup on macOS.
        # We return it directly rather than setting `size' because we don't
        # want to ensure it's valid in this special case.
        return QSize()

    minimum_size = self.minimumTabSizeHint(index)
    height = minimum_size.height()
    if self.vertical:
        confwidth = str(config.val.tabs.width)
        if confwidth.endswith("%"):
            main_window = objreg.get("main-window", scope="window", window=self._win_id)
            perc = int(confwidth.rstrip("%"))
            width = main_window.width() * perc / 100
        else:
            width = int(confwidth)
        size = QSize(max(minimum_size.width(), width), height)
    else:
        if config.val.tabs.pinned.shrink:
            pinned = self._tab_pinned(index)
            pinned_count, pinned_width = self._pinned_statistics()
        else:
            pinned = False
            pinned_count, pinned_width = 0, 0
        no_pinned_count = self.count() - pinned_count
        no_pinned_width = self.width() - pinned_width

        if pinned:
            # Give pinned tabs the minimum size they need to display their
            # titles, let Qt handle scaling it down if we get too small.
            width = self.minimumTabSizeHint(index, ellipsis=False).width()
        else:
            width = no_pinned_width / no_pinned_count

        # If no_pinned_width is not divisible by no_pinned_count, add a
        # pixel to some tabs so that there is no ugly leftover space.
        if no_pinned_count > 0 and index < no_pinned_width % no_pinned_count:
            width += 1

        # If we don't have enough space, we return the minimum size so we
        # get scroll buttons as soon as needed.
        width = max(width, minimum_size.width())

        size = QSize(width, height)
    qtutils.ensure_valid(size)
    return size