xmltodict library issue - Namespace separator ':' incompatible with Expat >=2.4.5 security fixes

[reinbach]

If you're seeing the following error on any card/transaction requests;

 File "/<removed>/lib/python3.8/site-packages/xmltodict.py", line 327, in parse
    parser.Parse(xml_input, True)
xml.parsers.expat.ExpatError: out of memory: line 1, column 0

And have Expat >= 2.4.5 installed, then see martinblech/xmltodict#289 for some insight.