Format to use for warning and error text output.
- plaintext
- Wikitext with HTML tags removed and entities replaced.
- wikitext
- Unparsed wikitext.
- html
- HTML.
- raw
- Message key and parameters.
- none
- No text output, only the error codes.
- bc
- Format used prior to MediaWiki 1.29. errorlang and errorsuselocal are ignored.