# Buggy code
def tab_move(self, index: typing.Union[str, int] = None, count=None):
    """Move the current tab according to the argument and [count].

    If neither is given, move it to the first position.

    Args:
        index: `+` or `-` to move relative to the current tab by
               count, or a default of 1 space.
               A tab index to move to that index.
        count: If moving relatively: Offset.
               If moving absolutely: New position (default: 0). This
               overrides the index argument, if given.
    """
    if index in ["+", "-"]:
        # relative moving
        new_idx = self._current_index()
        delta = 1 if count is None else count
        if index == "-":
            new_idx -= delta
        elif index == "+":  # pragma: no branch
            new_idx += delta

        if config.val.tabs.wrap:
            new_idx %= self._count()
    else:
        # absolute moving
        if count is not None:
            new_idx = count - 1
        elif index is not None:
            new_idx = index - 1 if index >= 0 else index + self._count()
        else:
            new_idx = 0

    if not 0 <= new_idx < self._count():
        raise cmdexc.CommandError("Can't move tab to position {}!".format(new_idx + 1))

    cur_idx = self._current_index()
    cmdutils.check_overflow(cur_idx, "int")
    cmdutils.check_overflow(new_idx, "int")
    self._tabbed_browser.tabBar().moveTab(cur_idx, new_idx)


# 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_move(self, index: typing.Union[str, int] = None, count=None):
    """Move the current tab according to the argument and [count].

    If neither is given, move it to the first position.

    Args:
        index: `+` or `-` to move relative to the current tab by
               count, or a default of 1 space.
               A tab index to move to that index.
        count: If moving relatively: Offset.
               If moving absolutely: New position (default: 0). This
               overrides the index argument, if given.
    """
    if index in ["+", "-"]:
        # relative moving
        new_idx = self._current_index()
        delta = 1 if count is None else count
        if index == "-":
            new_idx -= delta
        elif index == "+":  # pragma: no branch
            new_idx += delta

        if config.val.tabs.wrap:
            new_idx %= self._count()
    else:
        # absolute moving
        if count is not None:
            new_idx = count - 1
        elif index is not None:
            new_idx = index - 1 if index >= 0 else index + self._count()
        else:
            new_idx = 0

    if not 0 <= new_idx < self._count():
        raise cmdexc.CommandError("Can't move tab to position {}!".format(new_idx + 1))

    cur_idx = self._current_index()
    cmdutils.check_overflow(cur_idx, "int")
    cmdutils.check_overflow(new_idx, "int")
    self._tabbed_browser.widget.tabBar().moveTab(cur_idx, new_idx)