Add a new exception signal for ALL exceptions raised anywhere in application (#2724)

tests/test_signal_handlers.py

@@ -1,18 +1,19 @@
 import asyncio
 import os
 import signal
-
 from queue import Queue
 from types import SimpleNamespace
+from typing import Optional
 from unittest.mock import MagicMock
 
 import pytest
-
 from sanic_testing.testing import HOST, PORT
 
+from sanic import Sanic
 from sanic.compat import ctrlc_workaround_for_windows
-from sanic.exceptions import BadRequest
+from sanic.exceptions import BadRequest, ServerError
 from sanic.response import HTTPResponse
+from sanic.signals import Event
 
 
 async def stop(app, loop):
@@ -148,3 +149,26 @@ def test_signals_with_invalid_invocation(app):
         BadRequest, match="Invalid event registration: Missing event name"
     ):
         app.listener(stop)
+
+
+def test_signal_server_lifecycle_exception(app: Sanic):
+    trigger: Optional[Exception] = None
+
+    @app.route("/hello")
+    async def hello_route(request):
+        return HTTPResponse()
+
+    @app.signal(Event.SERVER_LIFECYCLE_EXCEPTION)
+    async def test_signal(exception: Exception):
+        nonlocal trigger
+        trigger = exception
+
+    @app.before_server_start
+    async def test_before_server_start(app):
+        raise ServerError("test_before_server_start")
+
+    with pytest.raises(ServerError, match="test_before_server_start"):
+        app.run(single_process=True)
+
+    assert isinstance(trigger, ServerError)
+    assert str(trigger) == "test_before_server_start"