'If a L{FlattenerError} is created with a L{Tag} instance with source
location information, the source location is included in the string
representation of the exception.'

def test_tag(self):

    tag = Tag('div', filename='/foo/filename.xhtml', lineNumber=17, columnNumber=12)
    self.assertEqual(str(FlattenerError(RuntimeError('reason'), [tag], [])), 'Exception    while    flattening:\n        File    "/foo/filename.xhtml",    line    17,    column    12,    in    "div"\nRuntimeError:    reason\n')
