Fix flake8 errors

.flake8

+[flake8]
+# E501: let black handle line length
+# W503 is incompatible with PEP 8
+ignore = E501,W503

migrations/env.py

@@ -3,6 +3,7 @@ from alembic import context
 from sqlalchemy import engine_from_config, pool
 from logging.config import fileConfig
 import logging
+from flask import current_app
 
 # this is the Alembic Config object, which provides
 # access to the values within the .ini file in use.
@@ -13,12 +14,6 @@ config = context.config
 fileConfig(config.config_file_name)
 logger = logging.getLogger("alembic.env")
 
-# add your model's MetaData object here
-# for 'autogenerate' support
-# from myapp import mymodel
-# target_metadata = mymodel.Base.metadata
-from flask import current_app
-
 config.set_main_option(
     "sqlalchemy.url", current_app.config.get("SQLALCHEMY_DATABASE_URI")
 )