Ubuntu – Cannot add any PPA

I recently tried to add PPA from this website.
I did sudo add-apt-repository ppa:canonical-qt5-edgers/qt5-proper from terminal.
I get an error saying

Cannot add PPA: 'ppa:canonical-qt5-edgers/qt5-proper'.
Please check that the PPA name or format is correct.

As suggested in other similar questions, I don't have any problem with internet connection because apt-get install is working as expected. This is not even PPA specific problem, I couldn't add other PPAs as well. This question says that I have to format the entire hard drive to solve this. I definitely cannot do that. Is this bug still unsolved?

I added the PPA line using Software Center. When it updates cache, it comes up with an error saying

W:GPG error: http://ppa.launchpad.net saucy Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F141B5F0C7122F9B, W:Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release i386 (20130424)/dists/raring/main/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
, W:Failed to fetch cdrom://Ubuntu 13.04 _Raring Ringtail_ - Release i386 (20130424)/dists/raring/restricted/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
, E:Some index files failed to download. They have been ignored, or old ones used instead.

Output of sudo add-apt-repository ppa:canonical-qt5-edgers/qt5-proper

Cannot add PPA: 'ppa:canonical-qt5-edgers/qt5-proper'.
Please check that the PPA name or format is correct.

How to solve this and what is the cause of this problem?

Thanks in advance.

OS: Ubuntu 13.10

AFTER EDIT: Before the edit, the question had PPA of Ubuntu SDK.After posting this, I realised that Ubuntu SDK is in the repositories of Ubuntu 13.10. Just thought, may be that's why I cannot add PPA. I tried next PPA and I came up with the same series of errors.