class RepoError(Exception):
    '''
    defining RepoError
    '''
    pass

class ValidError(Exception):
    '''
    defining ValidError
    '''
    pass

class UndoError(Exception):
    '''
    defining UndoError
    '''
    pass

class PickleRepoError(Exception):
    '''
    defining PickleRepoError
    '''
    pass

class FileRepoError(Exception):
    '''
    defining FileRepoError
    '''
    pass