Q:

apt-get update fails after upgrade

I just updated my Ubuntu from 12 to 13 doing:
apt-get update
...
apt-get upgrade

Next time, I should probably simply use instead:
apt-get dist-upgrade

My current version now is:
lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 13.04
Release:    13.04
Codename:   raring

When I tried to update the system gives me the error:
apt-get update
E: Type ‘sudo’ is not known on line 64 in source list /etc/apt/sources.list
E: The list of sources could not be read.

So I did a purge:
ppa-purge -purge *
Updating packages lists
E: Type ‘sudo’ is not known on line 64 in source list /etc/apt/sources.list
E: The list of sources could not be read.
Warning:  apt-get update failed for some reason
PPA to be removed: * urge
Warning:  Could not find package list for PPA: * urge

Went to sources:
cd /etc/apt
ls
apt.conf.d     sources.list.d            trustdb.gpg   trusted.gpg.d
preferences.d  sources.list.distUpgrade  trusted.gpg
sources.list   sources.list.save         trusted.gpg~

ls .*
.:
apt.conf.d     sources.list.d            trustdb.gpg   trusted.gpg.d
preferences.d  sources.list.distUpgrade  trusted.gpg
sources.list   sources.list.save         trusted.gpg~

..:
acpi                           logrotate.conf
adduser.conf                   logrotate.d
adjtime                        lsb-base
akonadi                        lsb-base-logging.sh
alternatives                   lsb-release
anacrontab                     ltrace.conf
apg.conf                       lvm
apm                            macfanctl.conf
apparmor                       magic
apparmor.d                     magic.mime
apport                         mailcap
apt                            mailcap.order
aptdaemon                      manpath.config
at.deny                        matchbox
at-spi2                        mime.types
avahi                          mke2fs.conf
bash.bashrc                    modprobe.d
bash_completion                modules
bash_completion.d              motd
bindresvport.blacklist         mtab
blkid.conf                     mtab.fuselock
blkid.tab                      mtools.conf
bluetooth                      mysql
brlapi.key                     nanorc
brltty                         netscsid.conf
brltty.conf                    network
ca-certificates                NetworkManager
ca-certificates.conf           networks
ca-certificates.conf.dpkg-old  newt
calendar                       nsswitch.conf
chatscripts                    obex-data-server
checkbox.d                     ODBCDataSources
colord.conf                    odbc.ini
compizconfig                   odbcinst.ini
ConsoleKit                     openal
console-setup                  openvpn
cracklib                       opt
cron.d                         os-release
cron.daily                     pam.conf
cron.hourly                    pam.d
cron.monthly                   papersize
crontab                        passwd
cron.weekly                    passwd-
crypttab                       pcmcia
cups                           perl
cupshelpers                    pkcs11
dbus-1                         pm
debconf.conf                   pnm2ppa.conf
debian_version                 polkit-1
default                        popularity-contest.conf
deluser.conf                   ppp
depmod.d                       printcap
dhcp                           profile
dhcp3                          profile.d
dictionaries-common            protocols
dkms                           pulse
dnsmasq.d                      purple
doc-base                       python
dpkg                           python2.7
drirc                          python3
emacs                          python3.2
environment                    python3.3
firefox                        qemu
fonts                          qemu-ifdown
foomatic                       qemu-ifup
foremost.conf                  rc0.d
fstab                          rc1.d
fstab.d                        rc2.d
fuse.conf                      rc3.d
gai.conf                       rc4.d
gconf                          rc5.d
gdb                            rc6.d
ghostscript                    rc.local
gimp                           rcS.d
gnome                          remote-login-service.conf
gnome-app-install              resolvconf
gnome-settings-daemon          resolv.conf
groff                          rmt
group                          rpc
group-                         rsyslog.conf
grub.d                         rsyslog.d
grub.d.bak                     samba
gshadow                        sane.d
gshadow-                       securetty
gtk-2.0                        security
gtk-3.0                        selinux
hdparm.conf                    sensors3.conf
host.conf                      sensors.d
hostname                       services
hosts                          sgml
hosts.allow                    shadow
hosts.deny                     shadow-
hp                             shells
icedtea-web                    signond.conf
ifplugd                        signon-ui
init                           skel
init.d                         snmp
initramfs-tools                speech-dispatcher
inputrc                        ssh
insserv                        ssl
insserv.conf                   subversion
insserv.conf.d                 sudoers
iproute2                       sudoers.d
issue                          sysctl.conf
issue.net                      sysctl.d
java-6-openjdk                 systemd
kbd                            terminfo
kde4                           thunderbird
kde4rc                         timezone
kernel                         ucf.conf
kernel-img.conf                udev
kerneloops.conf                udisks2
kernel-pkg.conf                ufw
ksysguarddrc                   updatedb.conf
kubuntu-default-settings       update-manager
kvm                            update-motd.d
ldap                           update-notifier
ld.so.cache                    UPower
ld.so.conf                     upstart-xsessions
ld.so.conf.d                   usb_modeswitch.conf
legal                          usb_modeswitch.d
libaudit.conf                  vim
libnl-3                        vtrgb
libpaper.d                     wgetrc
libreoffice                    wodim.conf
lightdm                        wpa_supplicant
lintianrc                      X11
locale.alias                   xdg
localtime                      xml
logcheck                       xul-ext
login.defs                     zsh_command_not_found    

As suggested, here is my sources.list:
# deb cdrom:[Ubuntu 12.10 _Quantal Quetzal_ - Release amd64 (20121017.5)]/ quantal main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://au.archive.ubuntu.com/ubuntu/ raring main restricted
deb-src http://au.archive.ubuntu.com/ubuntu/ raring main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://au.archive.ubuntu.com/ubuntu/ raring-updates main restricted
deb-src http://au.archive.ubuntu.com/ubuntu/ raring-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://au.archive.ubuntu.com/ubuntu/ raring universe
deb-src http://au.archive.ubuntu.com/ubuntu/ raring universe
deb http://au.archive.ubuntu.com/ubuntu/ raring-updates universe
deb-src http://au.archive.ubuntu.com/ubuntu/ raring-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://au.archive.ubuntu.com/ubuntu/ raring multiverse
deb-src http://au.archive.ubuntu.com/ubuntu/ raring multiverse
deb http://au.archive.ubuntu.com/ubuntu/ raring-updates multiverse
deb-src http://au.archive.ubuntu.com/ubuntu/ raring-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://au.archive.ubuntu.com/ubuntu/ raring-backports main restricted universe multiverse
deb-src http://au.archive.ubuntu.com/ubuntu/ raring-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu raring-security main restricted
deb-src http://security.ubuntu.com/ubuntu raring-security main restricted
deb http://security.ubuntu.com/ubuntu raring-security universe
deb-src http://security.ubuntu.com/ubuntu raring-security universe
deb http://security.ubuntu.com/ubuntu raring-security multiverse
deb-src http://security.ubuntu.com/ubuntu raring-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu quantal partner
# deb-src http://archive.canonical.com/ubuntu quantal partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu raring main
deb-src http://extras.ubuntu.com/ubuntu raring main

## for ArgoUML
# deb http://archive.getdeb.net/ubuntu/ oneiric-getdeb apps # disabled on upgrade to raring
deb http://archive.canonical.com/ lucid partner
deb-src http://archive.canonical.com/ lucid partner

# command line editor (nano)
sudo -e /etc/apt/sources.list

# graphical editor
gksu gedit /etc/apt/sources.list

Could anyone shed some light on it? Before upgrading, this problem did not exist.
I run my Ubuntu on a mac mini dual boot. It is meant to software development and client-server usage. Another machine, a laptop Acer running Mint, I tried to upgrade it but Mint does not allow you to upgrade from one distro release for the next, without a clean install. We also tried several tests with some other *nix flavours: FreeBSD, OpenBSD, CentOS, Fedora... and it came to a conclusion that Ubuntu looks to be the best option for a practical enterprise environment, with a good wide support for a large range of drivers, working also nicely both on rEFIt/rEFInd or Grub multi-booting.
Should I never upgrade Ubuntu Desktop from current distro to the next? Unless it is a Ubuntu LTS? So, is it the case that every new Ubuntu distro release requires a clean new install?
All comments and suggestions are highly appreciated.

A:

As shown, the last 5 lines in /etc/apt/sources.list should not be present:
# command line editor (nano)
sudo -e /etc/apt/sources.list

# graphical editor
gksu gedit /etc/apt/sources.list

Is that a mistake in your question, or the file?
The default 13.04 (raring) /etc/apt/sources.list file ends with:
## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu raring main
deb-src http://extras.ubuntu.com/ubuntu raring main

And then you have 4 lines to do with ArgoUML.

