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##### 11.7.2.3 Error Messaging

The back ends should use the function `nnheader-report` to report error conditions—they should not raise errors when they aren't able to perform a request. The first argument to this function is the back end symbol, and the rest are interpreted as arguments to `format` if there are multiple of them, or just a string if there is one of them. This function must always returns `nil`.

         (nnheader-report 'nnchoke "You did something totally bogus")

         (nnheader-report 'nnchoke "Could not request group %s" group)

Gnus, in turn, will call `nnheader-get-report` when it gets a `nil` back from a server, and this function returns the most recently reported message for the back end in question. This function takes one argument—the server symbol.

Internally, these functions access back-end`-status-string`, so the `nnchoke` back end will have its error message stored in `nnchoke-status-string`.