SQLAlchemy engine configuration is not passed to FAB based UI. Faced this issue when running Airflow with MySQL metadata store with wait_timeout = 120. Webserver is failing with Internal Server Error due to "[MySQL Server has gone away](https://docs.sqlalchemy.org/en/13/faq/connections.html#mysql-server-has-gone-away)" error. Settings like `sql_alchemy_pool_recycle` and  `sql_alchemy_pool_pre_ping` have no impact on FAB internal communication with MySQL.

**Apache Airflow version**: 1.10.12
airflow/settings.py
"""Initialize Airflow with all the settings from this file"""
    configure_vars()
    prepare_syspath()
    import_local_settings()
    global LOGGING_CLASS_PATH
    LOGGING_CLASS_PATH = configure_logging()
    configure_adapters()
    # The webservers import this file from models.py with the default settings.
    configure_orm()
    configure_action_logging()
    # Ensure we close DB connections at scheduler and gunicon worker terminations
    atexit.register(dispose_orm)
# pylint: enable=global-statement
# Const stuff
KILOBYTE = 1024
MEGABYTE = KILOBYTE * KILOBYTE
WEB_COLORS = {'LIGHTBLUE': '#4d9de0',
              'LIGHTORANGE': '#FF9933'}
# If store_serialized_dags is True, scheduler writes serialized DAGs to DB, and webserver
# reads DAGs from DB instead of importing from files.
STORE_SERIALIZED_DAGS = conf.getboolean('core', 'store_serialized_dags', fallback=False)
# Updating serialized DAG can not be faster than a minimum interval to reduce database
# write rate.
MIN_SERIALIZED_DAG_UPDATE_INTERVAL = conf.getint(
    'core', 'min_serialized_dag_update_interval', fallback=30)
# Fetching serialized DAG can not be faster than a minimum interval to reduce database