isAbstract.Class.RdChecks if a class is abstract or not. A class is abstract if it has abstract methods.
# S3 method for class 'Class'
isAbstract(this, ...)class().
  setConstructorS3().
  For more information see Class.
  if (isAbstract(RccViolationException))
    throw("The class RccViolationException should NOT be abstract.")