Installation problem on Ubuntu 16.04

Problem:
~$ sudo bash setup_frappe.sh --setup-production
Installing for Ubuntu xenial amd64
In case you encounter an error, you can post on https://discuss.frappe.io

Adding ubuntu mariadb repo
Installing packages for Ubuntu. This might take time…
Reading package lists…
Building dependency tree…
Reading state information…
build-essential is already the newest version (12.1ubuntu2).
fontconfig is already the newest version (2.11.94-0ubuntu1).
fontconfig set to manually installed.
git is already the newest version (1:2.7.4-0ubuntu1).
libssl-dev is already the newest version (1.0.2g-1ubuntu4).
libxext6 is already the newest version (2:1.3.3-1).
libxext6 set to manually installed.
libxrender1 is already the newest version (1:0.9.9-0ubuntu1).
libxrender1 set to manually installed.
libxslt1-dev is already the newest version (1.1.28-2.1).
libxslt1.1 is already the newest version (1.1.28-2.1).
libxslt1.1 set to manually installed.
xfonts-base is already the newest version (1:1.0.4+nmu1).
xfonts-base set to manually installed.
nodejs is already the newest version (4.2.6~dfsg-1ubuntu4).
The following packages were automatically installed and are no longer required:
checkbox-ng gstreamer1.0-clutter iproute libbind9-90 libc-ares2
libcamel-1.2-52 libcolamd2.8.0 libdiorite0.2 libdns100
libebook-contacts-1.2-1 libecal-1.2-18 libedata-cal-1.2-27
libedataserver-1.2-20 libenca0 libgee2 libglew1.10 libglewmx1.10 libgtop2-10
libimobiledevice4 libisc95 libisccc90 libisccfg90 libisl13 libllvm3.6v5
liblouis2 liblwres90 libnl-route-3-200 libntdb1 libpgm-5.1-0 libpoppler52
libpth20 libqpdf13v5 libraw10 libsodium13 libusbmuxd2 libv8-3.14.5
libx265-59 libzmq3 linux-headers-4.2.0-16 linux-headers-4.2.0-16-generic
linux-headers-4.2.0-23 linux-headers-4.2.0-23-generic linux-headers-4.2.0-25
linux-headers-4.2.0-25-generic linux-image-4.2.0-16-generic
linux-image-4.2.0-23-generic linux-image-4.2.0-25-generic
linux-image-extra-4.2.0-16-generic linux-image-extra-4.2.0-23-generic
linux-image-extra-4.2.0-25-generic python-cffi python-characteristic
python-dbus-dev python-ntdb python-ply python-pycparser python3-cffi
python3-checkbox-ng python3-ply python3-pycparser qml-module-qtquick-dialogs
qml-module-qtquick-localstorage qml-module-qtquick-privatewidgets
qtdeclarative5-localstorage-plugin qtdeclarative5-qtfeedback-plugin
qtdeclarative5-ubuntu-web-plugin telepathy-indicator unity-scope-audacious
unity-scope-clementine unity-scope-gmusicbrowser unity-scope-gourmet
unity-scope-guayadeque unity-scope-musique
Use ‘sudo apt autoremove’ to remove them.
The following additional packages will be installed:
libaio1 libcrypto++9v5 libdbd-mysql-perl libdbi-perl libexpat1-dev
libhtml-template-perl libjemalloc1 libmariadbclient18 libmysqlclient18
libmysqlclient20 libopts25 libpython-all-dev libpython-dev libpython2.7-dev
libreadline5 mariadb-client-10.0 mariadb-client-core-10.0
mariadb-server-10.0 mariadb-server-core-10.0 mysql-common nginx-common
nginx-core python-all python-all-dev python-meld3 python-pip-whl
python-wheel python2.7-dev redis-tools vim-runtime
Suggested packages:
libmldbm-perl libnet-daemon-perl libsql-statement-perl
libipc-sharedcache-perl libterm-readkey-perl mailx mariadb-test tinyca
fcgiwrap nginx-doc ntp-doc procmail postfix-mysql postfix-pgsql postfix-ldap
postfix-pcre sasl2-bin dovecot-common postfix-cdb postfix-doc
python-egenix-mxdatetime python-mysqldb-dbg python-setuptools-doc ruby-redis
iselect | screenie | byobu ncurses-term supervisor-doc ctags vim-doc
vim-scripts vim-gnome-py2 | vim-gtk-py2 | vim-gtk3-py2 | vim-athena-py2
| vim-nox-py2
The following NEW packages will be installed:
htop libaio1 libcrypto+±dev libcrypto++9v5 libdbd-mysql-perl libdbi-perl
libexpat1-dev libhtml-template-perl libjemalloc1 libmariadbclient-dev
libmariadbclient18 libmysqlclient18 libmysqlclient20 libopts25
libpython-all-dev libpython-dev libpython2.7-dev libreadline5
mariadb-client-10.0 mariadb-client-core-10.0 mariadb-common mariadb-server
mariadb-server-10.0 mariadb-server-core-10.0 mysql-common nginx nginx-common
nginx-core ntp postfix python-all python-all-dev python-dev python-meld3
python-mysqldb python-pip python-pip-whl python-setuptools python-wheel
python2.7-dev redis-server redis-tools screen supervisor vim vim-runtime
xfonts-75dpi
0 upgraded, 47 newly installed, 0 to remove and 0 not upgraded.
Need to get 61,4 MB of archives.
After this operation, 259 MB of additional disk space will be used.
WARNING: The following packages cannot be authenticated!
mysql-common mariadb-common libmysqlclient18 libmariadbclient18
mariadb-client-core-10.0 mariadb-client-10.0 mariadb-server-core-10.0
mariadb-server-10.0 libmariadbclient-dev mariadb-server
E: There were unauthenticated packages and -y was used without --allow-unauthenticated

System:
~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04 LTS
Release: 16.04
Codename: xenial

~$ python --version
Python 2.7.11+

~$ dpkg -l | grep pip
ii libpipeline1:amd64 1.4.1-2 amd64 pipeline manipulation library

Thanks in advance for any help or guidance you can give me, have a nice day!

ubuntu 16.04 installation (and whether it makes snese to go for that now) was discussed in this topic

maybe that’s helpful for you as well