home: Fix parsing bug for initial narrows.

There's more we'll want to do here, but this at least avoids error
emails when users attempt to misuse this interface.

zerver/tests/test_home.py

@@ -404,10 +404,10 @@ class HomeTest(ZulipTestCase):
     def test_bad_narrow(self) -> None:
         email = self.example_email("hamlet")
         self.login(email)
-        with patch('logging.exception') as mock:
+        with patch('logging.warning') as mock:
             result = self._get_home_page(stream='Invalid Stream')
         mock.assert_called_once()
-        self.assertEqual(mock.call_args_list[0][0][0], "Narrow parsing exception")
+        self.assertEqual(mock.call_args_list[0][0][0], "Invalid narrow requested, ignoring")
         self._sanity_check(result)
 
     def test_bad_pointer(self) -> None:

zerver/views/home.py

@@ -117,12 +117,13 @@ def home_real(request: HttpRequest) -> HttpResponse:
     narrow_topic = request.GET.get("topic")
     if request.GET.get("stream"):
         try:
+            # TODO: We should support stream IDs and PMs here as well.
             narrow_stream_name = request.GET.get("stream")
             (narrow_stream, ignored_rec, ignored_sub) = access_stream_by_name(
                 user_profile, narrow_stream_name)
             narrow = [["stream", narrow_stream.name]]
         except Exception:
-            logging.exception("Narrow parsing exception", extra=dict(request=request))
+            logging.warning("Invalid narrow requested, ignoring", extra=dict(request=request))
         if narrow_stream is not None and narrow_topic is not None:
             narrow.append(["topic", narrow_topic])