message: Making the error message more clear
diff: @@ -1541,10 +1541,13 @@ void Mesh::ReadGmshMesh(std::istream &input, int &curved, int &read_gf)
  if (phys_domain <= 0)
  {
  MFEM_ABORT("Non-positive element attribute in Gmsh mesh!\n"
  + "By default Gmsh sets element tags (attributes)"
  + " to '0' but MFEM requires that they be"
  + " positive integers.\n"
  "Use \"Physical Curve\", \"Physical Surface\","
  - " or \"Physical Volume\" to set attributes "
  + " or \"Physical Volume\" to set tags/attributes"
  " for all curves, surfaces, or volumes in your"
  - "Gmsh geometry.");
  + " Gmsh geometry to values which are >= 1.");
  }
  // initialize the mesh element
  @@ -1765,10 +1768,13 @@ void Mesh::ReadGmshMesh(std::istream &input, int &curved, int &read_gf)
  if (phys_domain <= 0)
  {
  MFEM_ABORT("Non-positive element attribute in Gmsh mesh!\n"
  + "By default Gmsh sets element tags (attributes)"
  + " to '0' but MFEM requires that they be"
  + " positive integers.\n"
  "Use \"Physical Curve\", \"Physical Surface\","
  - " or \"Physical Volume\" to set attributes "
  + " or \"Physical Volume\" to set tags/attributes"
  " for all curves, surfaces, or volumes in your"
  - "Gmsh geometry.");
  + " Gmsh geometry to values which are >= 1.");
  }
  // initialize the mesh element
  