This is not an error. It is a warning that fseventsd, which is Mac OS specific, cannot be installed on Linux.
There is no need to be alarmed, and the package that needs fsevents will still work - that's why it's an optional dependency.
Since many people are confused about this (particularly since this used to be a real error, not a warning) there's an open bug to make the current warning into an INFO instead
Additionally yarn already does this.
