Error out if user attempts to constrain a body particle
Error out if user attempts to constrain a body particle

The constraint mechanism in hoomd doesn't currently support constraining rigid bodies.
As such, constraint.sphere will now generate an error if asked to constrain a particle
belonging to a rigid body.
joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue