$ sudo add-apt-repository ppa:beineri/opt-qt55-trusty
Cannot add PPA: 'ppa:beineri/opt-qt55-trusty'.
Please check that the PPA name or format is correct.
Thanks ! Looks like I forgot to update the doc when fixing it for CI (eb5c158d8db1c61f84e2885be27e77594374e63b).
I'll update the doc for this one and #17 soon.