fix nested oneOf resolution with different schema types (fixes #232)

[fmigneault]

Allows a nested oneOf to refer to other schema types than object by considering the keyword expansion when needed.

Fixes

• fixes Invalid resolution of nested oneOf for schemas of differing types #232
• fix markdown package that uses __version_info__ in more recent versions instead of version_info
  (duplicate functionality as Handle removed markdown version_info #230)
• fix broken test that assumed default schema draft-04 not supported by new default in jsonschema

[fmigneault]

@cwacek Is it possible to consider this PR? If something should be adjusted, let me know.

[felixonmars]

Thanks for the PR. I am cherry-picking this into Arch Linux packaging to get around the following test failure:

=================================== FAILURES ===================================
________________________________ test_validates ________________________________

nested_arrays = {'properties': {'foo': {'items': {'items': [{'type': 'number'}, {'type': 'number'}], 'type': 'array'}, 'type': 'array'}}, 'title': 'example'}
instance = {'foo': [[42, 44]]}

    def test_validates(nested_arrays, instance):
>       validate(instance, nested_arrays)

test/test_nested_arrays.py:31:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
/usr/lib/python3.10/site-packages/jsonschema/validators.py:1117: in validate
    cls.check_schema(schema)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

cls = <class 'jsonschema.validators.Draft202012Validator'>
schema = {'properties': {'foo': {'items': {'items': [{'type': 'number'}, {'type': 'number'}], 'type': 'array'}, 'type': 'array'}}, 'title': 'example'}
format_checker = <FormatChecker checkers=['date', 'email', 'idn-email', 'ipv4', 'ipv6', 'regex', 'uuid']>

    @classmethod
    def check_schema(cls, schema, format_checker=_UNSET):
        Validator = validator_for(cls.META_SCHEMA, default=cls)
        if format_checker is _UNSET:
            format_checker = Validator.FORMAT_CHECKER
        validator = Validator(
            schema=cls.META_SCHEMA,
            format_checker=format_checker,
        )
        for error in validator.iter_errors(schema):
>           raise exceptions.SchemaError.create_from(error)
E           jsonschema.exceptions.SchemaError: [{'type': 'number'}, {'type': 'number'}] is not of type 'object', 'boolean'
E
E           Failed validating 'type' in metaschema['allOf'][1]['properties']['properties']['additionalProperties']['$dynamicRef']['allOf'][1]['properties']['items']['$dynamicRef']['allOf'][1]['properties']['items']['$dynamicRef']['allOf'][0]:
E               {'$defs': {'anchorString': {'pattern': '^[A-Za-z_][-A-Za-z0-9._]*$',
E                                           'type': 'string'},
E                          'uriReferenceString': {'format': 'uri-reference',
E                                                 'type': 'string'},
E                          'uriString': {'format': 'uri', 'type': 'string'}},
E                '$dynamicAnchor': 'meta',
E                '$id': 'https://json-schema.org/draft/2020-12/meta/core',
E                '$schema': 'https://json-schema.org/draft/2020-12/schema',
E                '$vocabulary': {'https://json-schema.org/draft/2020-12/vocab/core': True},
E                'properties': {'$anchor': {'$ref': '#/$defs/anchorString'},
E                               '$comment': {'type': 'string'},
E                               '$defs': {'additionalProperties': {'$dynamicRef': '#meta'},
E                                         'type': 'object'},
E                               '$dynamicAnchor': {'$ref': '#/$defs/anchorString'},
E                               '$dynamicRef': {'$ref': '#/$defs/uriReferenceString'},
E                               '$id': {'$comment': 'Non-empty fragments not allowed.',
E                                       '$ref': '#/$defs/uriReferenceString',
E                                       'pattern': '^[^#]*#?$'},
E                               '$ref': {'$ref': '#/$defs/uriReferenceString'},
E                               '$schema': {'$ref': '#/$defs/uriString'},
E                               '$vocabulary': {'additionalProperties': {'type': 'boolean'},
E                                               'propertyNames': {'$ref': '#/$defs/uriString'},
E                                               'type': 'object'}},
E                'title': 'Core vocabulary meta-schema',
E                'type': ['object', 'boolean']}
E
E           On schema['properties']['foo']['items']['items']:
E               [{'type': 'number'}, {'type': 'number'}]

/usr/lib/python3.10/site-packages/jsonschema/validators.py:231: SchemaError

[cwacek]

@felixonmars @fmigneault: apologies for the delay merging this in. I haven't had as much time as one would hope to maintain this repo. The updated package is released as 0.4.2

[fmigneault]

@cwacek
No worries. Thanks.