tests: server: incompatibility with aiohttp 3.9

Previously, the test suite repeatedly crashed in CI when running tests that
involved a browser disconnecting unexpectedly, such as the channels or bucket
tests. Seemingly, this started with the release of aiohttp 3.9 which
introduced web handler cancellation.

    https://docs.aiohttp.org/en/v3.9.0/web_advanced.html#web-handler-cancellation

Web handler cancellation means that aiohttp cancels the asyncio tasks of
aiohttp request handlers which encounter a `ConnectionClosedError`.
In Lona, the teardown code for connections gets called within aiohttp request
handlers, meaning that sometimes the connection teardown code does not run.

Web handler cancellation is an opt-in feature that is not enabled by default,
nor is it enabled by Lona. Although, it is enabled by pytest-aiohttp, which is
the reason it only crashes in CI.

As proposed in the aiohttp documentation, this patch adds a method to
`lona.Server` that shields all aiohttp request handlers from cancellation.

Signed-off-by: Florian Scherf <[email protected]>

lona/server.py

@@ -174,7 +174,7 @@ def __init__(self, project_root: str,
             '*', static_url, self._handle_static_file_request)
 
         self._app.router.add_route(
-            '*', '/{path_info:.*}', self._handle_http_request)
+            '*', '/{path_info:.*}', self._shielded_handle_http_request)
 
         # setup view loader
         server_logger.debug('setup view loader')
@@ -636,6 +636,18 @@ async def _handle_http_request(self, http_request):
 
         return self._render_response(response)
 
+    async def _shielded_handle_http_request(self, request):
+        """
+        Runs `Server._handle_http_request` shielded from cancelation
+
+        aiohttp 3.9 introduced web handler cancellation
+        (https://docs.aiohttp.org/en/v3.9.0/web_advanced.html#web-handler-cancellation)
+        which creates race conditions in the connections teardown code when
+        enabled.
+        """
+
+        return await asyncio.shield(self._handle_http_request(request))
+
     # public api ##############################################################
     @overload
     def run_coroutine_sync(