Better request cancel handling (#2513)

tests/test_cancellederror.py

@@ -0,0 +1,21 @@
+import asyncio
+
+from asyncio import CancelledError
+
+import pytest
+
+from sanic import Request, Sanic, json
+
+
+def test_can_raise_in_handler(app: Sanic):
+    @app.get("/")
+    async def handler(request: Request):
+        raise CancelledError("STOP!!")
+
+    @app.exception(CancelledError)
+    async def handle_cancel(request: Request, exc: CancelledError):
+        return json({"message": exc.args[0]}, status=418)
+
+    _, response = app.test_client.get("/")
+    assert response.status == 418
+    assert response.json["message"] == "STOP!!"

tests/test_middleware.py

@@ -166,7 +166,7 @@ def test_middleware_response_raise_cancelled_error(app, caplog):
     with caplog.at_level(logging.ERROR):
         reqrequest, response = app.test_client.get("/")
 
-        assert response.status == 503
+        assert response.status == 500
         assert (
             "sanic.error",
             logging.ERROR,