system_requirements() is not described as being a hook implementation

I think you're right. Good catch!

Patch for Drupal 8.

Looks good, thanks! I'll get this committed. Most likely I can use the same patch for D7 too.

Thanks! Committed to 8.x and 7.x.

In 6.x for consistency we should probably say "Implementation of.." rather than "Implements" (the rest of 6.x uses the old standard). So if someone still cares to port this to 6.x...

Backport to 6.x.

Thanks! But this patch is not quite right. Look at the 8.x/7.x patch on #2 -- we need to *replace* the existing function body.

The function body, everything within {}, is unchanged in patch on #2. I provided another patch to reflect the removed comments in #2 patch.

Thanks, that is the patch we needed. I will get it committed sometime soon.

Thanks! Committed to 6.x.