If you installed MySQL with XAMPP or LAMPP (the same thing), you need to change line 342 to call the command.  That's because LAMPP doesn't install MySQL to the default directory.  If you used the default installation of LAMPP, you should
change line 342 from:
/mysqldump --user=$USERNAME etc.
/opt/lampp/bin/mysqldump --user=$USERNAME etc.

If you installed LAMPP to some other directory you should obviously point to that directory instead.

This error stumped me for a little while, as I am new to Linux & MySQL.  I hope this saves somebody some time.