AutocompleteManager.deprecateForSuggestion is deprecated.

Autocomplete provider 'ClassProvider(undefined)'
returns suggestions with a `prefix` attribute.
The `prefix` attribute is now `replacementPrefix` and is optional.
See https://github.com/atom/autocomplete-plus/wiki/Provider-API
```
AutocompleteManager.deprecateForSuggestion (:11:646103)
o.push.Promise.resolve.then.o (:11:643877)
(null:null:null)
```

Start by locating the code that invokes AutocompleteManager.deprecateForSuggestion and the provider represented by ClassProvider(undefined). Read the linked Provider API documentation and trace where the prefix attribute is returned. Done means the provider uses optional replacementPrefix and no longer triggers this deprecation warning.

Written by the indexing model from the issue text.