[ci] Deprecate flake8 (#8409)

* [ci] Deprecate flake8

* Addressing @villebro's comments

superset/sql_lab.py

@@ -15,21 +15,21 @@
 # specific language governing permissions and limitations
 # under the License.
 # pylint: disable=C,R,W
+import logging
+import uuid
 from contextlib import closing
 from datetime import datetime
-import logging
 from sys import getsizeof
 from typing import Optional, Tuple, Union
-import uuid
 
 import backoff
-from celery.exceptions import SoftTimeLimitExceeded
-from contextlib2 import contextmanager
-from flask_babel import lazy_gettext as _
 import msgpack
 import pyarrow as pa
 import simplejson as json
 import sqlalchemy
+from celery.exceptions import SoftTimeLimitExceeded
+from contextlib2 import contextmanager
+from flask_babel import lazy_gettext as _
 from sqlalchemy.orm import sessionmaker
 from sqlalchemy.pool import NullPool