Backport PR #1233 on branch 1.x (Added error propagation to gateway_r…

…equest function) (#1234)Co-authored-by: Broden Wanner <[email protected]> Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Steven Silvester <[email protected]>

* Backport PR #1233: Added error propagation to gateway_request function

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: Broden Wanner <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Steven Silvester <[email protected]>

CHANGELOG.md

@@ -10,7 +10,7 @@ All notable changes to this project will be documented in this file.
 
 ### Bugs fixed
 
-- Backport PR #1212: Redact tokens, etc. in url parameters from request  logs [#1214](https://github.com/jupyter-server/jupyter_server/pull/1214) ([@blink1073](https://github.com/blink1073))
+- Backport PR #1212: Redact tokens, etc. in url parameters from request logs [#1214](https://github.com/jupyter-server/jupyter_server/pull/1214) ([@blink1073](https://github.com/blink1073))
 - Backport PR #1193: Fix get_loader returning None when load_jupyter_server_extension is not found (#1193) (#1199)Co-authored-by: Steven Silvester <[email protected]> Co-authored-by: pre-commit-ci\[bot\] \<66853113+pre-commit-ci\[bot\]@users.noreply.github.com> [#1199](https://github.com/jupyter-server/jupyter_server/pull/1199) ([@cmd-ntrf](https://github.com/cmd-ntrf))
 
 ### Documentation improvements

jupyter_server/gateway/gateway_client.py

@@ -506,9 +506,19 @@ async def gateway_request(endpoint: str, **kwargs: ty.Any) -> HTTPResponse:
     # NOTE: We do this here since this handler is called during the server's startup and subsequent refreshes
     # of the tree view.
     except HTTPClientError as e:
+        error_reason = f"Exception while attempting to connect to Gateway server url '{GatewayClient.instance().url}'"
+        error_message = str(e)
+        if e.response:
+            try:
+                error_payload = json.loads(e.response.body)
+                error_reason = error_payload.get("reason") or error_reason
+                error_message = error_payload.get("message") or error_message
+            except json.decoder.JSONDecodeError:
+                error_reason = e.response.body.decode()
+
         raise web.HTTPError(
             e.code,
-            f"Error attempting to connect to Gateway server url '{GatewayClient.instance().url}'.  "
+            f"Error from Gateway: [{error_message}] {error_reason}. "
             "Ensure gateway url is valid and the Gateway instance is running.",
         ) from e
     except ConnectionError as e: