Openapi-schema-validator

Changelog
- Validate oneOf, anyOf and allOf with discriminator (cherry-pick from 0.3.x) 30

Changelog
- Revert "make jsonschema4 compatible (DeprecationWarning fix)" 34
- Drop python 3.6 support (cherry-pick from 0.3.x and part 2) 35
- Limit jsonschema dependency 36

Changelog
* switch to poetry 27
* drop python 2.7 and 3.5 support 27 28
* make jsonschema4 compatible (DeprecationWarning fix) 25

Changelog
* Fix required in composition 16
* Prevent Schema Mutation 26

Changelog
* Stop assigning a version to our Validator (12)

Changelog
* Switch to a MIT-licensed dependency (4)
* Pypi license fix (10)