Error: Sub-process /usr/bin/dpkg returned an error code (1)

When a process locks the debconf config.dat file, you may get this error. 

The solution of this error is identifying the process and killing it. You can find the guilty process wtih this command: 

sudo fuser -v /var/cache/debconf/config.dat

You will get an PID on the screen. 

And you can use this PID in the following command:

sudo kill THAT_PID_NUMBER_GOT_ABOVE_COMMAND

or you can just use the following code to

kill the process without seeing PID number:

sudo fuser -v -k /var/cache/debconf/config.dat

All these info has been taken from askubuntu community.