message: In HypreParMatrix::ExtractSubmatrix, error out if hypre is
  built with CUDA without UVM -- this is required by the
  function hypre_ParCSRMatrixExtractSubmatrixFC, at least.
diff: @@ -1521,6 +1521,11 @@ HypreParMatrix * HypreParMatrix::Transpose() const
  HypreParMatrix *HypreParMatrix::ExtractSubmatrix(const Array<int> &indices,
  double threshold) const
  {
  +#if defined(HYPRE_USING_CUDA) && !defined(HYPRE_USING_UNIFIED_MEMORY)
  + MFEM_ABORT("This method requires HYPRE built with UVM when"
  + " HYPRE is using CUDA!");
  +#endif
  +
  if (!(A->comm))
  {
  hypre_MatvecCommPkgCreate(A);
  