fix fallback

superset/models/core.py

@@ -46,7 +46,7 @@
 from sqlalchemy.engine import Connection, Dialect, Engine
 from sqlalchemy.engine.reflection import Inspector
 from sqlalchemy.engine.url import URL
-from sqlalchemy.exc import ArgumentError
+from sqlalchemy.exc import ArgumentError, NoSuchModuleError
 from sqlalchemy.ext.hybrid import hybrid_property
 from sqlalchemy.orm import relationship
 from sqlalchemy.pool import NullPool
@@ -642,7 +642,11 @@ def db_engine_spec(self) -> Type[db_engine_specs.BaseEngineSpec]:
     @memoized
     def get_db_engine_spec(cls, url: URL) -> Type[db_engine_specs.BaseEngineSpec]:
         backend = url.get_backend_name()
-        driver = url.get_driver_name()
+        try:
+            driver = url.get_driver_name()
+        except NoSuchModuleError:
+            # can't load the driver, fallback for backwards compatibility
+            return db_engine_specs.BaseEngineSpec
 
         return db_engine_specs.get_engine_spec(backend, driver)