I have tried installing Grails using the answer found at Error Installing Grails - Unmet Dependencies :

sudo add-apt-repository ppa:groovy-dev/grails  
sudo apt-get update
sudo apt-get install grails-ppa

The first command returns without errors:

$ sudo add-apt-repository ppa:groovy-dev/grails
 Grails is an advanced and innovative open source web application platform that
 ...
 More info: 
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keyring `/tmp/tmpt59mo9/secring.gpg' created
gpg: keyring `/tmp/tmpt59mo9/pubring.gpg' created
gpg: requesting key 02A9EC29 from hkp server keyserver.ubuntu.com
gpg: /tmp/tmpt59mo9/trustdb.gpg: trustdb created
gpg: key 02A9EC29: public key "Launchpad PPA for Groovy Developers" imported
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)
OK

But the update command fails:

$ sudo apt-get update
...
Err  saucy/main amd64 Packages
  404  Not Found
Ign  saucy/main Translation-en_US
Ign  saucy/main Translation-en
W: Failed to fetch   404  Not Found

E: Some index files failed to download. They have been ignored, or old ones used instead.

Any idea why the ppa update fails with a 404 error?