Minor issue, but it appears that this library is using a deprecated method from SQLAlchemy:

great_expectations/datasource/fluent/sql_datasource.py:1238 SADeprecationWarning: The dbapi() classmethod on dialect classes has been renamed to import_dbapi(). Implement an import_dbapi() classmethod directly on class <class 'sqlalchemy_redshift.dialect.RedshiftDialect_psycopg2'> to remove this warning; the old .dbapi() classmethod may be maintained for backwards compatibility.
return sa.create_engine(connection_string, **kwargs)