python: Catch specific exceptions from requests.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

tools/lib/test_server.py

@@ -46,7 +46,7 @@ def server_is_up(server: "subprocess.Popen[bytes]", log_file: Optional[str]) ->
         # We could get a 501 error if the reverse proxy is up but the Django app isn't.
         # Note that zulipdev.com is mapped via DNS to 127.0.0.1.
         return requests.get('http://zulipdev.com:9981/accounts/home').status_code == 200
-    except Exception:
+    except requests.RequestException:
         return False
 
 @contextmanager