Initial release of the oVirt/RHV Engine API simulator.

Stateful FastAPI lab with contract packs, Compose/Helm, Docker Hub release
targets, and Pulumi coverage across all Engine series (GET/POST/PUT/DELETE/HEAD).

app/ovirt/errors.py

@@ -0,0 +1,68 @@
+"""oVirt Engine fault responses (XML/JSON)."""
+
+from __future__ import annotations
+
+from typing import Any
+
+from fastapi import Request
+from fastapi.responses import JSONResponse, Response
+
+
+class OVirtError(Exception):
+    def __init__(
+        self,
+        reason: str,
+        detail: str,
+        *,
+        status_code: int = 400,
+        code: str | None = None,
+    ) -> None:
+        super().__init__(detail)
+        self.reason = reason
+        self.detail = detail
+        self.status_code = status_code
+        self.code = code or reason
+
+
+def _wants_xml(request: Request) -> bool:
+    accept = (request.headers.get("accept") or "").lower()
+    content = (request.headers.get("content-type") or "").lower()
+    if "application/xml" in accept or "text/xml" in accept:
+        return True
+    if "json" in accept:
+        return False
+    if "xml" in content:
+        return True
+    # Engine default is XML when Accept is omitted / */*
+    return "json" not in accept
+
+
+def fault_body(error: OVirtError, *, as_xml: bool) -> str | dict[str, Any]:
+    if as_xml:
+        return (
+            '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
+            f"<fault><reason>{_esc(error.reason)}</reason>"
+            f"<detail>{_esc(error.detail)}</detail></fault>"
+        )
+    return {"fault": {"reason": error.reason, "detail": error.detail}}
+
+
+def _esc(value: str) -> str:
+    return (
+        value.replace("&", "&amp;")
+        .replace("<", "&lt;")
+        .replace(">", "&gt;")
+        .replace('"', "&quot;")
+    )
+
+
+async def ovirt_error_handler(request: Request, exc: OVirtError) -> Response:
+    as_xml = _wants_xml(request)
+    body = fault_body(exc, as_xml=as_xml)
+    if as_xml:
+        return Response(
+            content=str(body),
+            status_code=exc.status_code,
+            media_type="application/xml",
+        )
+    return JSONResponse(content=body, status_code=exc.status_code)