Getting '404 Not Found' error for ppa repository

[rajak7gmail]

Have installed python-pip, google-api-python-client & gdcmdtools are properly.
getting '404 Not Found' error for ppa files upon executing "apt-get update" cli after adding ppa repository.
From my browser I could able to access the ppa.launchpad.net url as well as I could able to reach the url's ip address from my terminal.
I am not sure why I am getting this error, kindly do the needful. your help is really appreciated.

root@raja-HP-Notebook:~# sudo apt-add-repository ppa:ctf/gdcmdtools
 Google Drive Command Line Tools

https://github.com/tienfuc/gdcmdtools
 More info: https://launchpad.net/~ctf/+archive/ubuntu/gdcmdtools
Press [ENTER] to continue or Ctrl-c to cancel adding it.

gpg: keybox '/tmp/tmp4j0e7tp6/pubring.gpg' created
gpg: /tmp/tmp4j0e7tp6/trustdb.gpg: trustdb created
gpg: key 8E81DA2218F1F430: public key "Launchpad PPA for TienFu Chen" imported
gpg: Total number processed: 1
gpg:               imported: 1
OK
root@raja-HP-Notebook:~# sudo apt-get update
Ign:1 http://dl.google.com/linux/chrome/deb stable InRelease
Get:2 http://security.ubuntu.com/ubuntu artful-security InRelease [78.6 kB]                                                                  
Ign:3 http://ppa.launchpad.net/ctf/gdcmdtools/ubuntu artful InRelease                                                                        
Hit:4 http://dl.google.com/linux/chrome/deb stable Release                                     
Hit:5 http://us.archive.ubuntu.com/ubuntu artful InRelease                                          
Err:7 http://ppa.launchpad.net/ctf/gdcmdtools/ubuntu artful Release                                 
  404  Not Found
Get:8 http://us.archive.ubuntu.com/ubuntu artful-updates InRelease [78.6 kB]
Get:9 http://us.archive.ubuntu.com/ubuntu artful-backports InRelease [72.2 kB]
Reading package lists... Done      
E: The repository 'http://ppa.launchpad.net/ctf/gdcmdtools/ubuntu artful Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:1 and /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:4
W: Target Packages (main/binary-i386/Packages) is configured multiple times in /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:1 and /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:4
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:1 and /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:4
W: Target Translations (main/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:1 and /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:4
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:1 and /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:4
W: Target DEP-11 (main/dep11/Components-amd64.yml) is configured multiple times in /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:1 and /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:4
W: Target DEP-11 (main/dep11/Components-all.yml) is configured multiple times in /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:1 and /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:4
W: Target DEP-11-icons (main/dep11/icons-64x64.tar) is configured multiple times in /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:1 and /etc/apt/sources.list.d/ctf-ubuntu-gdcmdtools-artful.list:4
root@raja-HP-Notebook:~# 
root@raja-HP-Notebook:~#