# Buggy code
def _run_userscript(self, selection, cmd, args, verbose):
    """Run a userscript given as argument.

    Args:
        cmd: The userscript to run.
        args: Arguments to pass to the userscript.
        verbose: Show notifications when the command started/exited.
    """
    env = {
        "QUTE_MODE": "command",
        "QUTE_SELECTED_TEXT": selection,
    }

    idx = self._current_index()
    if idx != -1:
        env["QUTE_TITLE"] = self._tabbed_browser.page_title(idx)

    # FIXME:qtwebengine: If tab is None, run_async will fail!
    tab = self._tabbed_browser.currentWidget()

    try:
        url = self._tabbed_browser.current_url()
    except qtutils.QtValueError:
        pass
    else:
        env["QUTE_URL"] = url.toString(QUrl.FullyEncoded)

    try:
        runner = userscripts.run_async(
            tab, cmd, *args, win_id=self._win_id, env=env, verbose=verbose
        )
    except userscripts.Error as e:
        raise cmdexc.CommandError(e)
    return runner


# 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 _run_userscript(self, selection, cmd, args, verbose):
    """Run a userscript given as argument.

    Args:
        cmd: The userscript to run.
        args: Arguments to pass to the userscript.
        verbose: Show notifications when the command started/exited.
    """
    env = {
        "QUTE_MODE": "command",
        "QUTE_SELECTED_TEXT": selection,
    }

    idx = self._current_index()
    if idx != -1:
        env["QUTE_TITLE"] = self._tabbed_browser.widget.page_title(idx)

    # FIXME:qtwebengine: If tab is None, run_async will fail!
    tab = self._tabbed_browser.widget.currentWidget()

    try:
        url = self._tabbed_browser.current_url()
    except qtutils.QtValueError:
        pass
    else:
        env["QUTE_URL"] = url.toString(QUrl.FullyEncoded)

    try:
        runner = userscripts.run_async(
            tab, cmd, *args, win_id=self._win_id, env=env, verbose=verbose
        )
    except userscripts.Error as e:
        raise cmdexc.CommandError(e)
    return runner