bpo-46811: Make test suite support Expat >=2.4.5 (pythonGH-31453) (pythonGH-31469)

Curly brackets were never allowed in namespace URIs
according to RFC 3986, and so-called namespace-validating
XML parsers have the right to reject them a invalid URIs.

libexpat >=2.4.5 has become strcter in that regard due to
related security issues; with ET.XML instantiating a
namespace-aware parser under the hood, this test has no
future in CPython.

References:
- https://datatracker.ietf.org/doc/html/rfc3968
- https://www.w3.org/TR/xml-names/

Also, test_minidom.py: Support Expat >=2.4.5
(cherry picked from commit 2cae938)

Co-authored-by: Sebastian Pipping <[email protected]>

Co-authored-by: Sebastian Pipping <[email protected]>

Author: 2 people

Misc/NEWS.d/next/Library/2022-02-20-21-03-31.bpo-46811.8BxgdQ.rst

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+Make test suite support Expat >=2.4.5