This is not a bug, you must remove /var/lib/mysql/debian-5.6.flag file
sudo -i rm /var/lib/mysql/debian-*.flag su {yourusername} sudo apt-get install mysql-server-5.5
This is not a bug, you must remove /var/lib/ mysql/debian- 5.6.flag file
sudo -i mysql/debian- *.flag
rm /var/lib/
su {yourusername}
sudo apt-get install mysql-server-5.5