message: Add node name to placer device-placement/kernel-assignment error messages .
diff: @@ -464,6 +464,7 @@ class ColocationGraph {
  // the user can see why an unsatisfiable placement occurred.
  std::unordered_map<string, string> type_to_devices;
  + std::vector<const Node*> colocation_nodes;
  int num_nodes_found = 0;
  for (const Node* node : graph_->nodes()) {
  @@ -475,6 +476,7 @@ class ColocationGraph {
  continue;
  }
  ++num_nodes_found;
  + colocation_nodes.push_back(node);
  const string& op_type = node->type_string();
  string devices_registered;
  for (const auto& device_type : members_[id].supported_device_types) {
  @@ -488,6 +490,13 @@ class ColocationGraph {
  for (const auto& td : type_to_devices) {
  strings::StrAppend(&text, "\n", td.first, ": ", td.second);
  }
  + strings::StrAppend(&text,
  + "\n\nColocation members and user-requested devices:");
  + for (const Node* node : colocation_nodes) {
  + strings::StrAppend(&text, "\n ", node->name(), " (", node->type_string(),
  + ") ", node->requested_device());
  + }
  + strings::StrAppend(&text, "\n");
  if (num_nodes_found <= 1) {
  text.clear();
  