class HttpForbidden(Exception):

  pass

class HttpNotFound(Exception):

  pass

class ModelException(Exception):

  pass

class ModelDeny(ModelException):

  pass

class ModelWrongData(ModelException):

  def __init__(self, messages = None):

    if messages is None:

      messages = list()

    if type(messages) is str:

      messages = [messages]

    assert(type(messages) is list)

    self.messages = messages

class ActionError(Exception):

  def __init__(self, messages = None):

    if messages is None:

      messages = list()

    if type(messages) is str:

      messages = [messages]

    assert(type(messages) is list)

    self.messages = messages