Bootstrap Directory Missing

Thanks @shigehiro, adding an extra line in a bootstrap_barrio custom theme fixed it (the last one, the other two already were there):

libraries-override:
  bootstrap_barrio/global-styling: false
  bootstrap_barrio/file: false
  bootstrap_barrio/bootstrap: false

I got another error (see #2986370: Library from basetheme should not be loaded from subtheme → ) removing line #2 above (bootstrap_barrio/file: false) fixed it.