Fix group encoding errors

  - TestEncoding.test_encode_unordered_content_2(): last test now
    raises the correct message (fixed index calculation for missing
    content tail)

xmlschema/tests/validation/test_encoding.py

@@ -371,12 +371,10 @@ def test_encode_unordered_content_2(self):
             expected=u'<A>\nhello<B1>abc</B1>\n<B2>10</B2>\n<B3>true</B3>\n</A>',
             indent=0, cdata_prefix='#'
         )
-        from xmlschema.converters import XMLSchemaConverter
-        # FIXME: UnorderedConverter do not work, an XMLSchemaValidationError is expected!!
         self.check_encode(
-            xsd_component=schema.elements['A'], converter=XMLSchemaConverter, unordered=True,
+            xsd_component=schema.elements['A'],
             data=ordered_dict_class([('B1', 'abc'), ('B2', 10), ('#1', 'hello')]),
-            expected=u'<A>\nhello<B1>abc</B1>\n<B2>10</B2>\n</A>', indent=0, cdata_prefix='#'
+            expected=XMLSchemaValidationError, indent=0, cdata_prefix='#'
         )
 
     def test_strict_trailing_content(self):

xmlschema/validators/groups.py

@@ -787,7 +787,7 @@ def iter_encode(self, element_data, validation='lax', **kwargs):
 
         if model.element is not None:
             for particle, occurs, expected in model.stop():
-                errors.append((index - cdata_index, particle, occurs, expected))
+                errors.append((index - cdata_index + 1, particle, occurs, expected))
 
         if children:
             if children[-1].tail is None: