Exception calling 'theme_boost_union_before_session_start'

line 200 of /cache/classes/factory.php: call to core_cache\factory->create_definition()
line 190 of /cache/classes/cache.php: call to core_cache\factory->create_cache_from_definition()
line 2364 of /theme/boost_union/locallib.php: call to core_cache\cache::make()
line 831 of /theme/boost_union/lib.php: call to theme_boost_union_manipulate_hooks()
line 900 of /lib/setup.php: call to theme_boost_union_before_session_start()
line 879 of /config.php: call to require_once()
line 28 of /mod/lesson/view.php: call to require_once()

Error

Configurar una sesión en la base de datos ha fallado. Por favor notifique al administrador del servidor.

Debug info:
Error code: dbsessionhandlerproblem

Stack trace:

line 66 of /lib/classes/session/database.php: core\session\exception thrown
line 149 of /lib/classes/session/manager.php: call to core\session\database->init()
line 136 of /lib/classes/session/manager.php: call to core\session\manager::start_session()
line 907 of /lib/setup.php: call to core\session\manager::start()
line 879 of /config.php: call to require_once()
line 28 of /mod/lesson/view.php: call to require_once()