Validate configtypes.Key correctly

qutebrowser/config/configtypes.py

@@ -1652,7 +1652,8 @@ class Key(BaseType):
         self._basic_py_validation(value, str)
         if not value:
             return None
-        #if utils.is_special_key(value):
-        #    value = '<{}>'.format(utils.normalize_keystr(value[1:-1]))
-        #return value
-        return keyutils.KeySequence.parse(value)
+
+        try:
+            return keyutils.KeySequence.parse(value)
+        except keyutils.KeyParseError as e:
+            raise configexc.ValidationError(value, str(e))

tests/unit/config/test_configtypes.py

@@ -2064,6 +2064,10 @@ class TestKey:
     def test_to_py_valid(self, klass, val, expected):
         assert klass().to_py(val) == expected
 
+    def test_to_py_invalid(self, klass):
+        with pytest.raises(configexc.ValidationError):
+            klass().to_py('\U00010000')
+
 
 @pytest.mark.parametrize('first, second, equal', [
     (re.compile('foo'), RegexEq('foo'), True),