sudo apt-get upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
  apport apport-gtk python3-apport python3-problem-report thunderbird
  thunderbird-gnome-support
6 to upgrade, 0 to newly install, 0 to remove and 0 not to upgrade.
Need to get 33.3 MB of archives.
After this operation, 301 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://mirror.netspace.net.au/pub/ubuntu/ trusty-updates/main python3-problem-report all 2.14.1-0ubuntu3.20 [9,714 B]
Get:2 http://mirror.netspace.net.au/pub/ubuntu/ trusty-updates/main python3-apport all 2.14.1-0ubuntu3.20 [75.4 kB]
Get:3 http://mirror.netspace.net.au/pub/ubuntu/ trusty-updates/main apport all 2.14.1-0ubuntu3.20 [182 kB]
Get:4 http://mirror.netspace.net.au/pub/ubuntu/ trusty-updates/main apport-gtk all 2.14.1-0ubuntu3.20 [9,526 B]
Get:5 http://mirror.netspace.net.au/pub/ubuntu/ trusty-updates/main thunderbird amd64 1:38.8.0+build1-0ubuntu0.14.04.1 [33.0 MB]
Get:6 http://mirror.netspace.net.au/pub/ubuntu/ trusty-updates/main thunderbird-gnome-support amd64 1:38.8.0+build1-0ubuntu0.14.04.1 [8,540 B]
Err http://mirror.netspace.net.au/pub/ubuntu/ trusty-security/main thunderbird amd64 1:38.8.0+build1-0ubuntu0.14.04.1
  Connection failed
Fetched 285 kB in 9s (30.5 kB/s)                                               
E: Failed to fetch http://mirror.netspace.net.au/pub/ubuntu/pool/main/t/thunderbird/thunderbird_38.8.0+build1-0ubuntu0.14.04.1_amd64.deb Connection failed

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