add-apt-repository command is suddenly very slow

There were no issues before, but today I started my computer and I removed the unstable OIBAF graphics drivers and tried to add stable OIBAF graphics PPA. I left for about 15 minutes and when I came back the terminal was stuck at the initial command without any output. It looked like this:

I thought this was an internet issue, but it wasn't. Then I canceled adding the PPA and tried to install it again but had the same issue (the apt-add-repository command does works but takes a lot of time to show any output. Everything was fine before --it took less than a minute to complete-- but now it takes more than 15 minutes).

I've also tried adding different PPAs but had the same issue.

My kernel version is 4.20.0

I've also built a kernel installed and removed but then there was no ppa related issue.

EDIT: There's more delay when I cancel the command with CTRL+C

Solution 1:

I found the issue, it was due to other unsigned repository I added to my system because of this there is a lot of delay in adding PPAs. Simply remove those unsigned PPAs and problem will be solved.