Secretary warns you against common problems; in this case, the Featured Image set for the post was too large in filesize.
Users define their editorial rules in YAML (see Settings -> Secretary) according to a number of built-in rule functions. For example, Secretary can show a warning if you’ve forgotten to set a Featured Image for your post, by adding the featured-image rule to your YAML config.
Secretary comes with a number of rules out of the box, but you can write your own custom plugins for Secretary by calling SecretaryRules::register. See example at https://github.com/ChrisBAshton/secretary-rule-gallery-at-top, and API documentation at https://github.com/ChrisBAshton/secretary.
Contact
If you spot any issues, or want to know how to contribute, please visit https://github.com/ChrisBAshton/secretary.
Please note that I have open-sourced this plugin to give back to the community, and do not have much spare time to answer support queries, but I’ll help where I can.