As a first step, line 51 in tests/test_gnucash_backend.py should be removed, its a cheat line:

SQLITE3 = XML

So that the tests that use sqllite actually end up using XML.
Test suite fails with that.

With SQLITE3 working, we should add a tests/test_gnucsh_backend_rdbms.py that using inheritance and overiding of the tests/test_gnucash_backend.py tests and does mysql and postgres with a tests username/password/database name, but is excluded from being run from setup.py seeing how most won't have that.

Once the lower level issues that these test reveals are addressed, we could add support in the bokeep default shell's config dialog to either allow entry of any gnucash backend URL (e.g. sqllite://... mysql:///...) or provide a four-way radio for the four backends with a separate u.i.; some other design or a mix of both.