escape_string() broken with Python 2.x

[jmuchemb]

$ python -c 'import MySQLdb; print(MySQLdb.escape_string(b"foo"))'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: must be impossible<bad format char>, not str
$ python3 -c 'import MySQLdb; print(MySQLdb.escape_string(b"foo"))'
b'foo'

Tested on Debian with version 1.3.4-1 (packaged in experimental), MariaDB 10.0.16-1 and Python 2.7.9-1
I also tried 1.3.5 but it's not better.

[methane]

Good catch!