dpkg: error: dpkg frontend lock is locked by another process
First, find out the id of the process that is holding the lock file:
lsof /var/lib/dpkg/lock-frontend
The above command will give you the PID of the processes using the lock files. Use this PID to kill the process:
sudo kill -9 PID
Now you can remove the lock and reconfigure dpkg:
sudo rm /var/lib/dpkg/lock-frontend
sudo dpkg --configure -a