test_pdb and test_sqlite3 readline completion tests fail on DragonFly and illumos

[serhiy-storchaka]

Some readline-based completion tests that drive input through a pseudo-terminal (test.support.pty_helper.run_pty) fail on DragonFly BSD and illumos, the same way they already fail on FreeBSD (gh-133558):

• test.test_pdb.PdbTestReadline.test_multiline_auto_indent
• test.test_pdb.PdbTestReadline.test_multiline_indent_completion (hangs)
• test.test_sqlite3.test_cli.Completion.test_complete_no_match

On these platforms GNU readline in the pseudo-terminal does not remove the auto-indentation when a backspace is sent, so multi-line input ends up with the wrong indentation, and the sqlite3 completion inserts literal tabs when there is no match.

Verified on VMs (all using the GNU readline backend):

Platform	Result
Linux	pass
NetBSD 10.1	pass
OpenBSD 7.9	pass
FreeBSD 15	fail (already skipped, gh-133558)
DragonFly 6.4	fail
illumos (Solaris)	fail

This is a platform readline behavior, not a CPython bug, so the fix is to extend the existing FreeBSD skips to DragonFly and Solaris.

Linked PRs

• gh-154279: Skip readline completion tests that fail on DragonFly and illumos #154280
• [3.15] gh-154279: Skip readline completion tests that fail on DragonFly and illumos (GH-154280) #154282
• [3.14] gh-154279: Skip readline completion tests that fail on DragonFly and illumos (GH-154280) #154288