[logging] deprecation notices for SQLite (#9662)

* [logging] deprecation notices for SQLite

* [logging] use warning for SQLite notice

* [logging] update grammar

superset/sql_lab.py

@@ -121,10 +121,14 @@ def get_query(query_id, session):
 @contextmanager
 def session_scope(nullpool):
     """Provide a transactional scope around a series of operations."""
-    if nullpool:
-        engine = sqlalchemy.create_engine(
-            app.config["SQLALCHEMY_DATABASE_URI"], poolclass=NullPool
+    database_uri = app.config["SQLALCHEMY_DATABASE_URI"]
+    if "sqlite" in database_uri:
+        logger.warning(
+            "SQLite Database support for metadata databases will be removed \
+            in a future version of Superset."
         )
+    if nullpool:
+        engine = sqlalchemy.create_engine(database_uri, poolclass=NullPool)
         session_class = sessionmaker()
         session_class.configure(bind=engine)
         session = session_class()