TypeError('expected string or bytes-like object')

[hmoffatt]

I get this exception when validating a test file:

from swagger_spec_validator import validate_spec_url
validate_spec_url('file:///home/hamish/tmp/swagger/test.yaml')

  File "/home/hamish/tmp/swagger/.pyvenv/lib/python3.9/site-packages/jsonschema/_utils.py", line 98, in find_additional_properties
    if patterns and re.search(patterns, property):
  File "/usr/lib/python3.9/re.py", line 201, in search
    return _compile(pattern, flags).search(string)
TypeError: expected string or bytes-like object

---
swagger: '2.0'

info:
  version: "0.0.0"
  title: Foo

schemes:
  - https

paths:
  /token/:
    post:
      summary: Login
      tags:
        - auth
      description: |
        Login and obtain an authorization token.
      responses:
        200:
          description: Authorization token
          schema:
            title: Token
            type: object