Under tox this test fail with:
```
File "voluptuous/tests.rst", line 47, in tests.rst
Failed example:
    schema({'two': 'two', 'one': 2})
Exception raised:
    Traceback (most recent call last):
      File "/usr/lib/python2.7/doctest.py", line 1289, in __run
        compileflags, 1) in test.globs
      File "<doctest tests.rst[11]>", line 1, in <module>
        schema({'two': 'two', 'one': 2})
      File "voluptuous/voluptuous/voluptuous.py", line 187, in __call__
        return self._compiled([], data)
      File "voluptuous/voluptuous/voluptuous.py", line 378, in validate_dict
        return base_validate(path, data.iteritems(), out)
      File "voluptuous/voluptuous/voluptuous.py", line 267, in validate_mapping
        raise MultipleInvalid(errors)
    MultipleInvalid: not a valid value for dictionary value @ data['one']
```