Legacy bsddb import tests fail (instead of skip) when the bsddb backend is unavailable

[eduralph]

Summary

gramps/plugins/test/imports_test.py legacy-database load tests hard-fail when the bsddb (Berkeley DB) backend cannot be loaded, instead of skipping. On any Linux environment without the berkeleydb/bsddb3 Python library installed, the whole-suite unit run reports new failures that are environmental, not code regressions.

Surfaced while running the gramps unit suite on maintenance/gramps61 (testbed harness) — previously masked by an unrelated headless-discovery segfault; once that is fixed the suite runs to completion and these reds appear.

Failing tests (7 observed)

5× gramps.plugins.test.imports_test.TestImports, all with the same cause:

False is not true : Cannot open database .../temp/imp_<ver> can't load database backend: 'bsddb'

• test_imp_3_4_5_zip, test_imp_4_1_3_zip, test_imp_4_2_8_zip, test_imp_5_0_1bsd_zip, test_imp_5_1_2bsd_zip

(Separately, test_WebCal and test_navwebpage in reports_test fail on web-report generation — likely a distinct issue; noted here only for completeness.)

Root cause

1. The bsddb backend plugin is still registered as STABLE — gramps/plugins/db/bsddb/bsddb.gpr.py (plg.status = STABLE, databaseclass = "DbBsddb").
2. It imports the underlying lib — gramps/plugins/db/bsddb/bsddb.py:33-35: from berkeleydb.db import ... with fallback from bsddb3.db import .... Neither berkeleydb nor bsddb3 is installed in modern environments, so the import (and thus make_database("bsddb")) fails.
3. The suite still ships legacy bsddb-format fixtures (imp_3.4.5.zip … imp_5.1.2bsd.zip) whose DBBACKEND marker reads bsddb.
4. db_load() reads the marker, calls make_database("bsddb"), the load fails → the test does assertTrue(False, ...).
5. The test only skips bsddb on Windows — imports_test.py (~L245): if dbid == "bsddb" and win(): self.skipTest("bsddb not supported on Windows"). There is no equivalent skip when the bsddb backend is simply unavailable on the platform.

Suggested fix

In db_load() (gramps/plugins/test/imports_test.py), skip when the bsddb backend cannot be loaded on any platform — e.g. generalize the existing Windows-only guard to detect an unavailable/unimportable bsddb backend (catch the load failure and self.skipTest(...)), rather than asserting failure. That keeps the legacy-format coverage where bsddb is present while not reddening environments where it has been dropped.

Notes

Not a release blocker for unrelated fixes — environmental. Filed for future work.