It seems like either a folder named `tfjs_model_data` already exists in your directory, or something has the `yolov2-tiny.h5` file open. Check the directory and worst case restart? Otherwise it’s a bit hard to tell what’s going on. You can also try asking in tfjs github repo as it seems to be an error with their tool.
As a tip, the trace would be a lot more readable if it was enclosed in tripe ticks ` ` `
your stuff here
` ` `
(without spaces inbetween the `).