4.7.1. ISO-10646 escapes
The \u and \U are 16 and 32 bit escapes
for ISO-10646 code points, requiring exactly 4 or 8 hexadecimal digits.
The expansion of these escapes in an 8 bit string is the UTF-8 encoding
of the corresponding code point. Note that '\xF0' and '\u00F0' are NOT
the same strings! The former consists of a single byte, value 0xF0,
the latter is a two byte UTF-8 sequence for the Latin-1 character with code
point 0xF0 (ETH), which is the two byte string '\xC3\xB0'.