message: Invoke MFEM_ABORT() if trying to use ParBlockNonlinearForm with face
  integrators - contributions from shared faces are not implemented yet.
diff: @@ -233,6 +233,11 @@ void ParBlockNonlinearForm::Mult(const Vector &x, Vector &y) const
  BlockNonlinearForm::MultBlocked(xs, ys);
  + if (fnfi.Size() > 0)
  + {
  + MFEM_ABORT("TODO: assemble contributions from shared face terms");
  + }
  +
  for (int s=0; s<fes.Size(); s++)
  {
  fes[s]->GetProlongationMatrix()->MultTranspose(
  @@ -291,6 +296,11 @@ BlockOperator & ParBlockNonlinearForm::GetGradient(const Vector &x) const
  GetLocalGradient(x); // gradients are stored in 'Grads'
  + if (fnfi.Size() > 0)
  + {
  + MFEM_ABORT("TODO: assemble contributions from shared face terms");
  + }
  +
  for (int s1=0; s1<fes.Size(); s1++)
  {
  for (int s2=0; s2<fes.Size(); s2++)
  