Adapt "no subjectaltname" test for service-identitity >= 24

[jlaine]

When a certificate contains no subjectAltName extension, service-identity now raises a CertificateError instead of a VerificationError.

[jlaine]

@rthalley I'm not entirely comfortable with this code, because extract_patterns could also raise an Exception.

I think I'd be more comfortable with exactly two errors paths:

• CertificateError => use str(exc)
• VerificationError => f"Certificate subjectAltName does not match {hostname}."

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (20cd4ee) 100.00% compared to head (9dd2b96) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #452 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 25 25 Lines 4881 4881 ========================================= Hits 4881 4881 ```

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[rthalley]

You could also go for "belt and braces" and just fall back to the first exception if extract_patterns raises, e.g.

try:
    patterns = service_identity.cryptography.extract_patterns(certificate)
except Exception:
    patterns = []
if len(patterns) == 0:
     errmsg = str(exc)

[jlaine]

I'm going to merge as-is after thinking about it, we can always revisit this.