check-swagger-sources.py is not run in CI

[anoadragon453]

check-swagger-sources.py is a validation script that ensures the OpenAPI YAML is valid and that constraints are met.

Currently the script is failing with:

Traceback (most recent call last):
  File "/home/user/code/matrix-doc/./scripts/check-swagger-sources.py", line 185, in <module>
    check_swagger_file(path)
  File "/home/user/code/matrix-doc/./scripts/check-swagger-sources.py", line 107, in check_swagger_file
    check_response(filepath, request, code, response)
  File "/home/user/code/matrix-doc/./scripts/check-swagger-sources.py", line 85, in check_response
    raise ValueError("Error validating JSON schema for %r %r" % (
ValueError: ("Error validating JSON schema for 'GET /initialSync' 200", <ValidationError: "'event_id' is a required property">)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/user/code/matrix-doc/./scripts/check-swagger-sources.py", line 187, in <module>
    raise ValueError("Error checking file %s" % (path,), e)
ValueError: ('Error checking file /home/user/code/matrix-doc/data/api/client-server/old_sync.yaml', ValueError("Error validating JSON schema for 'GET /initialSync' 200", <ValidationError: "'event_id' is a required property">)

which will need to be fixed before it can land in CI. Edit: the breakage is tied to matrix-org/matrix-spec-proposals@36b02ed.

It can be run by simply installing the dependencies from scripts/requirements.txt and then running with python scripts/check-swagger-sources.py.