MultiLineStr causes UnicodeDecodeError under Python 2.x

[jmafc]

As reported by Josep Martinez:

Given a view with accented characters in its definition text, e.g., with the word 'Jurídico', dbtoyaml causes an error in pyYAML such as the following:

UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 98: ordinal not in range(128)

The i with acute accent is U+00ED, but it's encoded as 0xc3ad in UTF-8. The problem does not occur under Python 3.x or under Python 2.x but prior to the change f13980d which introduced MultiLineStr.