After #2762 we get a deprecation warning in tests:

/home/runner/work/python-tuf/python-tuf/.tox/py/lib/python3.13/site-packages/urllib3/_request_methods.py:182: DeprecationWarning: URLs without a scheme (ie 'https://') are deprecated and will raise an error in a future version of urllib3. To avoid this DeprecationWarning ensure all URLs start with 'https://' or 'http://'. Read more in this issue: urllib3/urllib3#2920

According to NicholasTanz tests in the code base were intentionally using no scheme/host to trigger error handling logic. Let's silence the warning somehow -- or possibly remove the schemeless test?