Add py-prance 0.15.0
Prance provides parsers for Swagger/OpenAPI 2.0 and 3.0 API specifications in
Python. It uses flex, swagger_spec_validator or openapi_spec_validator to
validate specifications, but additionally resolves JSON references in accordance
with the OpenAPI spec.
Mostly the latter involves handling non-URI references; OpenAPI is fine with
providing relative file paths, whereas JSON references require URIs at this
point in time.