bugfix: get_session() contextmgr usage in consume_signals()

[wssheldon]

Resolves:

AttributeError-'_GeneratorContextManager' object has no attribute 'query'

on

    install_plugins()
    db_session = get_session()
    organizations = get_all_organizations(db_session=db_session)

---> 

def get_all(*, db_session) -> List[Optional[Organization]]:
    """Gets all organizations."""
    return db_session.query(Organization)   <---