fix: handle non-IANA HTTP status codes without crashing

[adeev-mardia]

Problem

Generated clients crash with ValueError when the server returns a non-IANA HTTP status code such as:

• 520 – Cloudflare "Web Server Returned an Unknown Error"
• 561 – AWS WAF / Application Load Balancer unauthorized
• 499 – nginx "Client Closed Request"

The crash happens inside _build_response in every generated endpoint module:

def _build_response(...):
    return Response(
        status_code=HTTPStatus(response.status_code),  # ValueError on 520, 561, 499
        ...
    )

http.HTTPStatus is a closed IntEnum — it only accepts IANA-registered codes. Any code outside that set raises ValueError.

This is a silent runtime failure: users see an unhandled exception even though their API call succeeded.

Fixes #1442.

Changes

openapi_python_client/templates/endpoint_module.py.jinja

Replace the bare HTTPStatus(response.status_code) call with a try/except that falls back to the raw integer:

# Before
status_code=HTTPStatus(response.status_code),

# After
try:
    status_code = HTTPStatus(response.status_code)
except ValueError:
    status_code = response.status_code

openapi_python_client/templates/types.py.jinja

Widen the Response.status_code type annotation to accept both known and unknown codes:

# Before
status_code: HTTPStatus

# After
status_code: HTTPStatus | int

Why this approach?

• Zero breaking change — HTTPStatus is a subclass of int, so all existing code that compares response.status_code == 200 or response.status_code == HTTPStatus.OK continues to work without modification.
• No new public API — unlike the opt-in flag proposed in Support non standard http codes #1407, this just makes the default path not crash.
• Minimal diff — two template files, two targeted changes.

Testing

To reproduce the crash before this fix:

from http import HTTPStatus
HTTPStatus(520)  # ValueError: 520 is not a valid HTTPStatus

After the fix, _build_response returns a Response with status_code=520 (plain int) instead of raising.