failed to send WATCHDOG=1 notification message: Transport endpoint is not connected

Update ubuntu properly. Write following commands in terminal:

sudo apt-get update
update-manager

After completion update, Write following command in terminal:

reboot

Hopefully, Problem will be solved.
If the problem is still exits:

• Press and Hold Power button and let the PC to turn off forcibly.
• Turn on PC now, it will on perfectly.
• if it throws fsck error, write command:
  fsck -yf /dev/sdaX 
  Done