In one of my dev sites I've a wrong unoconv version and in the environment page I'm getting:

Invalid get_string() identifier: 'unoconvwarning' or component 'admin'. Perhaps you are missing $string['unoconvwarning'] = ''; in lang/en/admin.php?

Tracing down the problems, it seems that the string was removed by MDL-57618 (haven't looked how that string ended in the deprecated section of the file, it shouldn't be there because it's still in use).

So this issue is, simply, about to add the string back (master only). Easy one