text: class AlreadySignedUpException(Exception):
      role: str
  
      def __init__(self, message, role):
          self.role = role
          super().__init__(message)
  
  
  class RosterFullException(Exception):
      pass
  
  
  class EventNotFoundException(Exception):
      pass
  
  
  class InvalidTrialName(Exception):
      pass
  
  
  class InvalidRoleName(Exception):
      pass
  