Improve NPMplus HTTP error details

services/npmplus.py

@@ -48,7 +48,17 @@ def _request_json(
         with urlopen(req, timeout=10, context=context) as resp:
             payload = resp.read().decode("utf-8")
     except HTTPError as e:
-        raise RuntimeError(f"HTTP {e.code}") from e
+        detail = f"HTTP {e.code}"
+        try:
+            payload = e.read().decode("utf-8").strip()
+        except Exception:
+            payload = ""
+        if payload:
+            payload = " ".join(payload.split())
+            if len(payload) > 300:
+                payload = payload[:300] + "..."
+            detail = f"{detail}: {payload}"
+        raise RuntimeError(f"{detail} ({url})") from e
     except URLError as e:
         raise RuntimeError(str(e.reason)) from e