From what I understand PY2 supports utf-8 encoding (see: https://docs.python.org/2/library/codecs.html#standard-encodings), and if implemented the only draw back will be: "The unicode() constructor has the signature unicode(string[, encoding, errors]). All of its arguments should be 8-bit strings. The first argument is converted to Unicode using the specified encoding; if you leave off the encoding argument, the ASCII encoding is used for the conversion, so characters greater than 127 will be treated as errors" (https://docs.python.org/2/howto/unicode.html#the-unicode-type)
Python 2 documentation suggests, "The most important tip is: Software should only work with Unicode strings internally, converting to a particular encoding on output." (https://docs.python.org/2/howto/unicode.html#tips-for-writing-unicode-aware-programs)
I do not see a problem with deriving from UnicodeMixin.
@Lokal_Profil do you have tests written for the BaseLink Class?

The patch above was submitted by @Morgan11235 @mstucky @Zkhalido @Mph8318

New to the project, but I can give this a try.