python_version and registryAlias

[evilensky]

How are you running Renovate?

A Mend.io-hosted app

Which platform you running Renovate on?

GitHub.com

Which version of Renovate are you using?

43.36.2

Please tell us more about your question or problem

We are encountering

WARN: Custom registries are not allowed for this datasource and will be ignored
{
  "datasource": "python-version",
  "registryUrls": [
    "https://myjfrogregistry.jfrog.io/myjfrogregistry/api/pypi/pypi/simple"
  ],
  "defaultRegistryUrls": null
}

To the best of my knowledge we are not setting this anywhere but our global configuration:

  "python": {
    "registryUrls": ["https://myjfrogregistry.jfrog.io/myjfrogregistry/api/pypi/pypi/simple"]
  },

I need a bit to sanitize the full log but I am wondering if the customRegistry is being incorrectly merged into the python-version depName, and if so, if Renovate should be filtering this package by default?

Logs (if relevant)

Logs

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