# Buggy code
def __str__(self):
    """Convert this KeyInfo to a meaningful name.

    Return:
        A name of the key (combination) as a string.
    """
    key_string = _key_to_string(self.key)
    modifiers = int(self.modifiers)

    if self.key in _MODIFIER_MAP:
        # Don't return e.g. <Shift+Shift>
        modifiers &= ~_MODIFIER_MAP[self.key]
    elif _is_printable(self.key):
        # "normal" binding
        if not key_string:  # pragma: no cover
            raise ValueError("Got empty string for key 0x{:x}!".format(self.key))

        assert len(key_string) == 1, key_string
        if self.modifiers == Qt.ShiftModifier:
            assert not is_special(self.key, self.modifiers)
            return key_string.upper()
        elif self.modifiers == Qt.NoModifier:
            assert not is_special(self.key, self.modifiers)
            return key_string.lower()
        else:
            # Use special binding syntax, but <Ctrl-a> instead of <Ctrl-A>
            key_string = key_string.lower()

    # "special" binding
    assert is_special(self.key, self.modifiers)
    modifier_string = _modifiers_to_string(modifiers)
    return "<{}{}>".format(modifier_string, key_string)


# 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 __str__(self):
    """Convert this KeyInfo to a meaningful name.

    Return:
        A name of the key (combination) as a string.
    """
    key_string = _key_to_string(self.key)
    modifiers = int(self.modifiers)

    if self.key in _MODIFIER_MAP:
        # Don't return e.g. <Shift+Shift>
        modifiers &= ~_MODIFIER_MAP[self.key]
    elif _is_printable(self.key):
        # "normal" binding
        if not key_string:  # pragma: no cover
            raise ValueError("Got empty string for key 0x{:x}!".format(self.key))

        assert len(key_string) == 1, key_string
        if self.modifiers == Qt.ShiftModifier:
            assert not is_special(self.key, self.modifiers)
            return key_string.upper()
        elif self.modifiers == Qt.NoModifier:
            assert not is_special(self.key, self.modifiers)
            return key_string.lower()
        else:
            # Use special binding syntax, but <Ctrl-a> instead of <Ctrl-A>
            key_string = key_string.lower()

    # "special" binding
    assert is_special(self.key, self.modifiers) or self.modifiers == Qt.KeypadModifier
    modifier_string = _modifiers_to_string(modifiers)
    return "<{}{}>".format(modifier_string, key_string)