Union employee Robert Davis filed a lawsuit Monday in an effort to remove Roy Roberts, the emergency manager for Detroit Public Schools, because he did not take the oath of office before he started working in the position.While the lawsuit is asking the removal of the leader of the state’s largest school district on what could be considered a technicality, Davis filed a similar lawsuit that led to the removal of an elected school board member in Highland Park in 2008.Gov. Rick Snyder appointed Roberts to run DPS in May. Roberts took the oath of office in August and filed the paperwork with the Michigan Secretary of State.