Fix the following traceback:
```
/usr/users/ga002/soranzon/software/galaxyproject_galaxy/scripts/db_shell.py in printquery(statement, bind)
60 if bind is None:
61 bind = statement.session.get_bind(
---> 62 statement._mapper_zero_or_none())
63 statement = statement.statement
64 elif bind is None:
AttributeError: 'Query' object has no attribute '_mapper_zero_or_none'
```
due to the removal of `_mapper_zero_or_none()` in SQLAlchemy commit
https://github.com/sqlalchemy/sqlalchemy/commit/234a5b9723fbbb9747c0f9e3917baf8500b73370