Python3 typeerror:a Bytes-like object is required

Error when running Telnetlib: Typeerror:a Bytes-like object is required and not ' str ' due to differences in Python2 and Python3 versions.
It works in Python2, and the most important new feature of Python3 is the clearer distinction between text and binary data. Text is encoded in Unicode and is of type STR, while binary data is bytes type.

Python has two types of conversion functions encode (), decode ().

Encode (encoded), the STR type can be encoded as bytes.
Decode (decoding), you can convert the bytes type to the str type.

Therefore, you need to use encode () when interacting with Telnetlib.

Tn.read_until ("Username:". Encode ())

Python3 typeerror:a Bytes-like object is required