Package check result: ERROR

Check: examples, Result: ERROR
  Running examples in ‘mlr3fairness-Ex.R’ failed
  The error most likely occurred in:
  
  > base::assign(".ptime", proc.time(), pos = "CheckExEnv")
  > ### Name: groupwise_metrics
  > ### Title: Evaluate a metric on each protected subgroup in a task.
  > ### Aliases: groupwise_metrics
  > 
  > ### ** Examples
  > 
  >   library("mlr3")
  >   t = tsk("compas")
  >   l = lrn("classif.rpart")
  Warning: Package 'rpart' required but not installed for Learner 'classif.rpart'
  >   m = groupwise_metrics(msr("classif.acc"), t)
  >   l$train(t)$predict(t)$score(m, t)
  Error: The following packages could not be loaded: rpart
  Execution halted