can't concat str to bytes

As an AI language model, I don't have the context of your code to give you a specific solution, but I can explain the error message you received.

This error message occurs when you try to concatenate a string and bytes object in Python. In Python 3, strings are Unicode objects by default, while bytes objects represent raw binary data. They are two different types and cannot be concatenated directly.

To fix this error, you need to convert the bytes object to a string using the `decode()` method or convert the string to bytes using the `encode()` method.

For example, if you have a bytes object `b"hello"` and a string `" world"`, you can convert the bytes object to a string and concatenate them like this:

b"hello".decode() + " world"

Or you can convert the string to bytes and concatenate them like this:

b"hello" + " world".encode()

Hope this helps!