Display helpful error message on deadlock

from alembic.script import ScriptDirectory

from alembic.script.base import Script

from sqlalchemy import create_engine

from sqlalchemy.exc import OperationalError

from galaxy.model import Base

from galaxy.model.migrations import (

        literal_binds=True,

        dialect_opts={"paramstyle": "named"},

    )

    with context.begin_transaction():

        context.run_migrations()

    _run_migrations()

def _configure_and_run_migrations_online(url) -> None:

    engine = create_engine(url)

    with engine.connect() as connection:

        context.configure(connection=connection, target_metadata=target_metadata)

        _run_migrations()

    engine.dispose()

def _run_migrations():

    with context.begin_transaction():

        try:

            context.run_migrations()

    engine.dispose()

        except OperationalError as error:

            if getattr(error.orig, "pgcode", None) == "40P01":  # PostgreSQL DeadlockDetected error detected

                msg = """A deadlock has been detected. This may be due to a database

revision requiring exclusive access to a database object. To avoid this error, it is recommended to

shut down all Galaxy procesess during database migration."""

                log.error(msg)

                raise

def _get_url_from_config() -> str: