'Check that is_zipfile() correctly identifies non-zip files.'

def test_is_zip_erroneous_file(self):

    with open(TESTFN, 'w') as fp:
        fp.write('this    is    not    a    legal    zip    file\n')
    chk = zipfile.is_zipfile(TESTFN)
    self.assertFalse(chk)
    with open(TESTFN, 'rb') as fp:
        chk = zipfile.is_zipfile(fp)
        self.assertTrue((not chk))
    fp = StringIO()
    fp.write('this    is    not    a    legal    zip    file\n')
    chk = zipfile.is_zipfile(fp)
    self.assertTrue((not chk))
    fp.seek(0, 0)
    chk = zipfile.is_zipfile(fp)
    self.assertTrue((not chk))
