Fantastic Fiction is a known plugin.
I would speculate that you did once download it and it failed, or is out of date.
If it's
only showing up in the jobs output, I would further speculate that maybe you have a confused/damaged Calibre install that is some how partially using code or executables for another, older Calibre install.
I vaguely recall that happening before, and I know that I've had Windows become confused start using book reader from older, portable versions when double clicking say .epub files.
Repair or uninstall/re-install of Calibre may help. YMMV, this is outside my area of knowledge.