Update your sh file path :
*/10 * * * * /var/mysqlbackup.sh > /var/log/yourloggilename.log
Note: log file must have 755 permissions.
content of mysqlbackup.sh:
echo "Running.."
cd /usr/local/bin
echo "backup file is creating...."
python mysqlbackup.py --cnf /etc/my.cnf --todir /var/backup
echo "backup file created"