Query Gurobi attributes from JuMP model

[aahaselgrove]

I would like to query the optimality gap after my solver has completed execution. The Gurobi website indicates that this is an attribute of the solution (https://www.gurobi.com/documentation/6.5/refman/mipgap.html), but I can't see how to query this from a JuMP model (or, for that matter, from a Gurobi Model).

[odow]

General support is about to drop: #247

But for now,

using JuMP, Gurobi
model = Model(with_optimizer(Gurobi.Optimizer))
# ...
optimize!(model)
MOI.get(model, MOI.RelativeGap())

The JuMP docs should be updated.