raj@linode:~$ sudo apt-get install quassel-core
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  libpcre16-3 libqca-qt5-2 libqca-qt5-2-plugins libqt5core5a libqt5dbus5 libqt5network5 libqt5script5 libqt5sql5 libqt5sql5-sqlite qttranslations5-l10n
The following NEW packages will be installed:
  libpcre16-3 libqca-qt5-2 libqca-qt5-2-plugins libqt5core5a libqt5dbus5 libqt5network5 libqt5script5 libqt5sql5 libqt5sql5-sqlite qttranslations5-l10n quassel-core
0 upgraded, 11 newly installed, 0 to remove and 71 not upgraded.
Need to get 2,670 kB/5,818 kB of archives.
After this operation, 26.2 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Err:1 http://mirrors.linode.com/ubuntu xenial-updates/main amd64 libqt5core5a amd64 5.5.1+dfsg-16ubuntu7.2
  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]
Err:2 http://mirrors.linode.com/ubuntu xenial-updates/main amd64 libqt5dbus5 amd64 5.5.1+dfsg-16ubuntu7.2
  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]
Err:3 http://mirrors.linode.com/ubuntu xenial-updates/main amd64 libqt5network5 amd64 5.5.1+dfsg-16ubuntu7.2
  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]
Err:4 http://mirrors.linode.com/ubuntu xenial-updates/main amd64 libqt5sql5 amd64 5.5.1+dfsg-16ubuntu7.2
  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]
Err:5 http://mirrors.linode.com/ubuntu xenial-updates/main amd64 libqt5sql5-sqlite amd64 5.5.1+dfsg-16ubuntu7.2
  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]
E: Failed to fetch http://mirrors.linode.com/ubuntu/pool/main/q/qtbase-opensource-src/libqt5core5a_5.5.1+dfsg-16ubuntu7.2_amd64.deb  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]

E: Failed to fetch http://mirrors.linode.com/ubuntu/pool/main/q/qtbase-opensource-src/libqt5dbus5_5.5.1+dfsg-16ubuntu7.2_amd64.deb  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]

E: Failed to fetch http://mirrors.linode.com/ubuntu/pool/main/q/qtbase-opensource-src/libqt5network5_5.5.1+dfsg-16ubuntu7.2_amd64.deb  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]

E: Failed to fetch http://mirrors.linode.com/ubuntu/pool/main/q/qtbase-opensource-src/libqt5sql5_5.5.1+dfsg-16ubuntu7.2_amd64.deb  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]

E: Failed to fetch http://mirrors.linode.com/ubuntu/pool/main/q/qtbase-opensource-src/libqt5sql5-sqlite_5.5.1+dfsg-16ubuntu7.2_amd64.deb  404  Not Found [IP: 2600:3c03:1::45a4:df28 80]

E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?