'If a L{FlattenerError} is created with a string root, up to around 40
bytes from that string are included in the string representation of the
exception.'

def test_string(self):

    self.assertEqual(str(error.FlattenerError(RuntimeError('reason'), ['abc123xyz'], [])), "Exception    while    flattening:\n        'abc123xyz'\nRuntimeError:    reason\n")
    self.assertEqual(str(error.FlattenerError(RuntimeError('reason'), [('0123456789' * 10)], [])), "Exception    while    flattening:\n        '01234567890123456789<...>01234567890123456789'\nRuntimeError:    reason\n")
