# Buggy code
def tab_only(self, prev=False, next_=False, force=False):
    """Close all tabs except for the current one.

    Args:
        prev: Keep tabs before the current.
        next_: Keep tabs after the current.
        force: Avoid confirmation for pinned tabs.
    """
    cmdutils.check_exclusive((prev, next_), "pn")
    cur_idx = self._tabbed_browser.currentIndex()
    assert cur_idx != -1

    def _to_close(i):
        """Helper method to check if a tab should be closed or not."""
        return not (i == cur_idx or (prev and i < cur_idx) or (next_ and i > cur_idx))

    # close as many tabs as we can
    first_tab = True
    pinned_tabs_cleanup = False
    for i, tab in enumerate(self._tabbed_browser.widgets()):
        if _to_close(i):
            if force or not tab.data.pinned:
                self._tabbed_browser.close_tab(tab, new_undo=first_tab)
                first_tab = False
            else:
                pinned_tabs_cleanup = tab

    # Check to see if we would like to close any pinned tabs
    if pinned_tabs_cleanup:
        self._tabbed_browser.tab_close_prompt_if_pinned(
            pinned_tabs_cleanup,
            force,
            lambda: self.tab_only(prev=prev, next_=next_, force=True),
            text="Are you sure you want to close pinned tabs?",
        )


# 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 tab_only(self, prev=False, next_=False, force=False):
    """Close all tabs except for the current one.

    Args:
        prev: Keep tabs before the current.
        next_: Keep tabs after the current.
        force: Avoid confirmation for pinned tabs.
    """
    cmdutils.check_exclusive((prev, next_), "pn")
    cur_idx = self._tabbed_browser.widget.currentIndex()
    assert cur_idx != -1

    def _to_close(i):
        """Helper method to check if a tab should be closed or not."""
        return not (i == cur_idx or (prev and i < cur_idx) or (next_ and i > cur_idx))

    # close as many tabs as we can
    first_tab = True
    pinned_tabs_cleanup = False
    for i, tab in enumerate(self._tabbed_browser.widgets()):
        if _to_close(i):
            if force or not tab.data.pinned:
                self._tabbed_browser.close_tab(tab, new_undo=first_tab)
                first_tab = False
            else:
                pinned_tabs_cleanup = tab

    # Check to see if we would like to close any pinned tabs
    if pinned_tabs_cleanup:
        self._tabbed_browser.tab_close_prompt_if_pinned(
            pinned_tabs_cleanup,
            force,
            lambda: self.tab_only(prev=prev, next_=next_, force=True),
            text="Are you sure you want to close pinned tabs?",
        )