Alembic database freshness check.

check.py

from alembic import config
from alembic import script
from alembic.runtime import migration
import sqlalchemy

import exceptions


engine = sqlalchemy.create_engine(DATABASE_URL)
alembic_cfg = config.Config('alembic.ini')
script_ = script.ScriptDirectory.from_config(alembic_cfg)
with engine.begin() as conn:
    context = migration.MigrationContext.configure(conn)
    if context.get_current_revision() != script_.get_current_head():
        raise exceptions.DatabaseIsNotUpToDate('Upgrade the database.')

Above was published in Alembic Cookbook and improved/updated over time: https://alembic.sqlalchemy.org/en/latest/cookbook.html#test-current-database-revision-is-at-head-s