Here's how I solved it:
Start the docker container for the application in an interactive mode, in my case it an nginx container :
docker run -i -t nginx:latest /bin/bash
Run the command below to grant read permission to the others role for the resolv.conf file:
chmod o+r /etc/resolv.conf
Note: If you are having this issue on your host machine (Ubuntu Linux OS) and not for the Docker containers, then run the same command adding sudo to it in the host machine terminal:
sudo chmod o+r /etc/resolv.conf
Endeavour to exit your bash interactive terminal once you run this:
exit
And then open a new bash interactive terminal and run the commands again:
apt-get update
apt-get install nano
export TERM=xterm
Everything should work fine now.
Reference to this on Digital Ocean: Apt error: Temporary failure resolving 'deb.debian.org'
That's all.
I hope this helps