CLI: ensure verdi database version works even if schema outdated (#…

…4641)

The command was failing if the database schema was out of sync because
the backend was loaded, through `get_manager`, with the default schema
check on. Since the database does not actually have to be used, other
than to retrieve the current schema version and generation, we can load
the backend without the check.

aiida/cmdline/commands/cmd_database.py

@@ -31,7 +31,9 @@ def database_version():
     """
     from aiida.manage.manager import get_manager
 
-    backend_manager = get_manager().get_backend_manager()
+    manager = get_manager()
+    manager._load_backend(schema_check=False)  # pylint: disable=protected-access
+    backend_manager = manager.get_backend_manager()
 
     echo.echo('Generation: ', bold=True, nl=False)
     echo.echo(backend_manager.get_schema_generation_database())