This message is not needed because the IDP chooser page will take
care of the case where a browser-based authorization flow did not
request any specific IDP. For browserless flows (only allowed for
the `pinniped-cli` client), the client must request a specific IDP
(except in backwards-compatibility mode) because there is no browser
in which to show the IDP chooser page. Failing to request a specific
IDP in a browserless flow will result in a helpful error message
being returned.
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