`custom_check` function removed in version 3.2 but release notes don't mention it

[gene1wood]

It looks like the custom_check function was removed in bd6fbfc96dac1f66854e6807b7cfd4b5825f3ad6 as part of the v3.2 release.

You may want to add to the release notes that this function isn't present anymore, maybe in the Cleanups section and mention it as a potentially breaking change. I discovered this in Diaoul/subliminal#1013 which uses the custom_check function.