python - Pythons 2.7.x docs about Unicode and why this still works?

Question

According to the Python 2.7.x documentation:

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:

   >>> unicode('abcdef' + chr(255))    
   Traceback (most recent call last):
   ...
   UnicodeDecodeError: 'ascii' codec can't decode byte 0xff in position 6:
   ordinal not in range(128)

So why does this work with Japanese characters in it?:

TestStr = "サーバ移設"
print TestStr
サーバ移設

and why does this work too?:

TestStr = unicode("サーバ移設")
print TestStr
サーバ移設

I would have expected an unicode decode error since the Japanese characters are not within the 8bit string range.