Invalid variable name results in confusing MultiAdaptorNoDataError

[robmarkcole]

Is your feature request related to a problem? Please describe.

Example below:

import cdsapi

dataset = "reanalysis-era5-land-monthly-means"
request = {
    "product_type": ["monthly_averaged_reanalysis"],
    "variable": ["tp"], # total_precipitation
    "year": ["2025"],
    "month": ["07"],
    "time": ["00:00"],
    "data_format": "netcdf",
    "download_format": "unarchived",
    "area": "global"
}

client = cdsapi.Client()
client.retrieve(dataset, request).download()

Raises error:

---------------------------------------------------------------------------
HTTPError                                 Traceback (most recent call last)
Cell In[11], [line 2](vscode-notebook-cell:?execution_count=11&line=2)
      1 client = cdsapi.Client()
----> [2](vscode-notebook-cell:?execution_count=11&line=2) client.retrieve(dataset, request).download()

File ~/gitlab/climate-data-store/.venv/lib/python3.11/site-packages/ecmwf/datastores/legacy_client.py:167, in LegacyClient.retrieve(self, name, request, target)
    165 submitted: datastores.Remote | datastores.Results
    166 if self.wait_until_complete:
--> [167](https://file+.vscode-resource.vscode-cdn.net/Users/robin.cole/gitlab/climate-data-store/~/gitlab/climate-data-store/.venv/lib/python3.11/site-packages/ecmwf/datastores/legacy_client.py:167)     submitted = self.client.submit_and_wait_on_results(
    168         collection_id=name,
    169         request=request,
    170     )
    171 else:
    172     submitted = self.client.submit(
    173         collection_id=name,
    174         request=request,
    175     )

File ~/gitlab/climate-data-store/.venv/lib/python3.11/site-packages/ecmwf/datastores/client.py:414, in Client.submit_and_wait_on_results(self, collection_id, request)
    398 def submit_and_wait_on_results(
    399     self, collection_id: str, request: dict[str, Any]
    400 ) -> datastores.Results:
    401     """Submit a request and wait for the results to be ready.
    402 
...
    100 response.raise_for_status()

HTTPError: 400 Client Error: Bad Request for url: https://cds.climate.copernicus.eu/api/retrieve/v1/jobs/7e7c72fc-2191-4cd6-86f0-18fa957435d2/results
The job has failed
The job failed with: MultiAdaptorNoDataError

Describe the solution you'd like

Suggest a more informative error description, or the library could handle validation of variables

Describe alternatives you've considered

No response

Additional context

No response

Organisation

No response