'Match the date format from xgettext for POT-Creation-Date'

@unittest.skipIf(sys.platform.startswith('aix'), 'bpo-29972:    broken    test    on    AIX')
def test_POT_Creation_Date(self):

    from datetime import datetime
    with temp_cwd(None) as cwd:
        assert_python_ok(self.script)
        with open('messages.pot') as fp:
            data = fp.read()
        header = self.get_header(data)
        creationDate = header['POT-Creation-Date']
        if creationDate.endswith('\\n'):
            creationDate = creationDate[:(- len('\\n'))]
        datetime.strptime(creationDate, '%Y-%m-%d    %H:%M%z')
