Why is `clean_str` present in `wikienv`?

[jamesbraza]

I am finding certain strings can break clean_str:

p = "This is a test string with unicode escape: \\u00e9"

This will break clean_str:

UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe9 in position 43: unexpected end of data

Why do we need to convert string to be UTF-8? And if it's required, why not just ignore conversion errors?