# Buggy code
def item_focus(self, which):
    # This duplicates some completion code, but I don't see a nicer way...
    assert which in ["prev", "next"], which
    selmodel = self._file_view.selectionModel()

    parent = self._file_view.rootIndex()
    first_index = self._file_model.index(0, 0, parent)
    row = self._file_model.rowCount(parent) - 1
    last_index = self._file_model.index(row, 0, parent)

    if not first_index.isValid():
        # No entries
        return

    assert last_index.isValid()

    idx = selmodel.currentIndex()
    if not idx.isValid():
        # No item selected yet
        idx = last_index if which == "prev" else first_index
    elif which == "prev":
        idx = self._file_view.indexAbove(idx)
    else:
        assert which == "next", which
        idx = self._file_view.indexBelow(idx)

    # wrap around if we arrived at beginning/end
    if not idx.isValid():
        idx = last_index if which == "prev" else first_index

    selmodel.setCurrentIndex(
        idx, QItemSelectionModel.ClearAndSelect | QItemSelectionModel.Rows
    )
    self._insert_path(idx, clicked=False)


# 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 item_focus(self, which):
    # This duplicates some completion code, but I don't see a nicer way...
    assert which in ["prev", "next"], which
    selmodel = self._file_view.selectionModel()

    parent = self._file_view.rootIndex()
    first_index = self._file_model.index(0, 0, parent)
    row = self._file_model.rowCount(parent) - 1
    last_index = self._file_model.index(row, 0, parent)

    if not first_index.isValid():
        # No entries
        return

    assert last_index.isValid()

    idx = selmodel.currentIndex()

    if not idx.isValid():
        # No item selected yet
        idx = last_index if which == "prev" else first_index
    elif which == "prev":
        idx = self._file_view.indexAbove(idx)
    else:
        assert which == "next", which
        idx = self._file_view.indexBelow(idx)

    # wrap around if we arrived at beginning/end
    if not idx.isValid():
        idx = last_index if which == "prev" else first_index

    idx = self._do_completion(idx, which)

    selmodel.setCurrentIndex(
        idx, QItemSelectionModel.ClearAndSelect | QItemSelectionModel.Rows
    )
    self._insert_path(idx, clicked=False)