$ sudo apt-get install libffi-dev
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  libffi-dev
0 upgraded, 1 newly installed, 0 to remove and 125 not upgraded.
Need to get 116 kB of archives.
After this operation, 304 kB of additional disk space will be used.
WARNING: The following packages cannot be authenticated!
  libffi-dev
Install these packages without verification [y/N]? y
Err http://us-west-2.ec2.archive.ubuntu.com/ubuntu/ raring/main libffi-dev amd64 3.0.13-2ubuntu1
  404  Not Found [IP: 91.189.92.201 80]
Failed to fetch http://us-west-2.ec2.archive.ubuntu.com/ubuntu/pool/main/libf/libffi/libffi-dev_3.0.13-2ubuntu1_amd64.deb  404  Not Found [IP: 91.189.92.201 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?