use django aliases for ranges to support psycopg 2 and 3

[jsatt]

Django 4.2 introduces support for psycopg 3, but when using psycopg 3 Ranges without psycopg2 install, pyling-django raises an AstroidImportError due to apply_type_shim checking for psycopg2._range. Django 4.2 also now provides aliases to the Ranges in the appropriate library. This change uses these aliases for checking and falls back using psycopg2 if they are not available (running Django <4.2).

[michael-k]

I tried your branch, but now I run into a different problem. The field is defined as period = DateRangeField(null=False, blank=False) and we use period.lower/period.upper. With psycopg3, pylint complains that Instance of 'DateRangeField' has no 'lower' member (no-member) (same for uppper).

• Range.lower/.upper in psycopg2
• Range.lower/upper in psycopg3 (The only difference I can see is the Generic[T].)

Can you please include psycop3 variants of external_psycopg2_noerror_postgres_fields.py and external_psycopg2_noerror_postgres_fields.rc in this PR?

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I've also tried period[0]/period[1] with psycopg3 and pylint complains that Value 'self.period' is unsubscriptable (unsubscriptable-object).

• Django: 4.2.10 and 5.0.2
• psycopg: 3.1.18

[carlio]

I have added the tests suggested and merged this in, to find out if they work ; if not I will fix things up. Thanks!