[3.15] gh-154303: Skip test_sqlite3 CLI completion tests on OpenBSD (GH-154304) (GH-154305)

OpenBSD's readline does not honor "completion-query-items 0", so completing
many candidates blocks on a "Display all N?" prompt that hangs the
pseudo-terminal opened by run_pty().  Skip the whole Completion class on
OpenBSD, like the existing libedit skip.
(cherry picked from commit 63b564f)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: 3 people

Lib/test/test_sqlite3/test_cli.py

@@ -223,6 +223,9 @@ def setUpClass(cls):
         readline = import_module("readline")
         if readline.backend == "editline":
             raise unittest.SkipTest("libedit readline is not supported")
+        if sys.platform.startswith("openbsd"):
+            # OpenBSD's readline does not honor "completion-query-items 0".
+            raise unittest.SkipTest("OpenBSD readline hangs on completion")
 
     def write_input(self, input_, env=None):
         script = textwrap.dedent("""