and then there were none. The closing words of this well-known nursery rhyme should dispel the notion that none can only take a singular verb. People opposing the plural use base their argument on the fact that none comes from the Old English word an, meaning one. But the citational evidence against restricting none is overwhelming. None has been used as both a singular and plural pronoun since the ninth century.
§ 39. none. 1. Grammar. The American Heritage Book of English Usage. 1996
Student or Learner