The URL is https://[2001:db8::17]/, the server is running with a certificate that includes both DNS:2001:db8::17 and IP:2001:db8::17 as alt_names. Accessing that URL with e.g. curl works just fine, when using urllib3 I am seeing this error instead:

A problem was encountered with the certificate that prevented urllib3 from finding the SubjectAlternativeName field. This can affect certificate validation. The error was Codepoint U+003A at position 5 of u'2001:db8::17' not allowed