Maybe I'm reading the diff wrong, but it looks to me like you have: utils.execute('mkfs.ext3', '-l', fs_label, '-F', target)
where you'd want: utils.execute('mkfs.ext3', '-L', fs_label, '-F', target)
Specifically, the flag for label is upper case L , not lower case.
Maybe I'm reading the diff wrong, but it looks to me like you have: execute( 'mkfs.ext3' , '-l', fs_label, '-F', target)
utils.
where you'd want: execute( 'mkfs.ext3' , '-L', fs_label, '-F', target)
utils.
Specifically, the flag for label is upper case L , not lower case.