message: TF server should not crash when -v=1 is enabled.
  These WriteTextProto() calls are purely for diagnostics (and are usually called within IF_VLOG_IS_ON(1) guards), but if they fail to write to a file, they'll take down the entire calling process.  Which makes debugging difficult, and seems rather astonishing.
diff: @@ -63,7 +63,12 @@ string MakeUniquePath(string name) {
  string DumpGraphDefToFile(const string& name, GraphDef const& graph_def) {
  string path = MakeUniquePath(name);
  - TF_CHECK_OK(WriteTextProto(Env::Default(), path, graph_def));
  + Status status = WriteTextProto(Env::Default(), path, graph_def);
  + if (!status.ok()) {
  + VLOG(1) << "Failed to dump GraphDef to file: " << path << " : " << status;
  + path.clear();
  + path = "(unavailable)";
  + }
  return path;
  }
  @@ -79,7 +84,13 @@ string DumpGraphToFile(const string& name, Graph const& graph,
  string DumpFunctionDefToFile(const string& name, FunctionDef const& fdef) {
  string path = MakeUniquePath(name);
  - TF_CHECK_OK(WriteTextProto(Env::Default(), path, fdef));
  + Status status = WriteTextProto(Env::Default(), path, fdef);
  + if (!status.ok()) {
  + VLOG(1) << "Failed to dump FunctionDef to file: " << path << " : "
  + << status;
  + path.clear();
  + path = "(unavailable)";
  + }
  return path;
  }
  