Insufficient guidance when operation fails with 'requires user authentication' error

While trying to use vsts to create a work item, I get an error that

```
The requested resource requires user authentication: https://azurenpt.int.thomson.com/tfs/_apis Please see https://aka.ms/vsts-cli-auth for more information.
```

But the error doesn't tell me what authentication is missing. The `vsts login` completed without error. I'm able to create work items using the web interface. My token has permissions to create a work item.

It would be helpful to indicate what is not correct so users can resolve issues like these.

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* ID: 9c63192e-dc64-73c4-8c9d-f3854cf0887b
* Version Independent ID: 7c6632f8-8208-3779-2b6f-cc86bb1bce7d
* Content: [Get started with the VSTS CLI](https://docs.microsoft.com/en-us/cli/vsts/get-started?view=vsts-cli-latest)
* Content Source: [latest/docs-ref-conceptual/get-started.md](https://github.com/MicrosoftDocs/vsts-docs-cli-python/blob/live/latest/docs-ref-conceptual/get-started.md)
* Product: **vsts**
* Technology: **vsts**
* GitHub Login: @elbatk
* Microsoft Alias: **elbatk**