'Test that the presolver removes constraints with no variables.'

def test_presolve_constant_constraints(self):

    x = Variable()
    obj = Maximize(sqrt(x))
    prob = Problem(obj, [(Constant(2) <= 2)])
    data = prob.get_problem_data(s.ECOS)
    A = data['A']
    G = data['G']
    for row in range(A.shape[0]):
        assert (A[row, :].nnz > 0)
    for row in range(G.shape[0]):
        assert (G[row, :].nnz > 0)
