How to fix perforce error 'Some file(s) could not be transferred from client.'

Problem:
open for read: c:\p4\client_spec.txt: The system cannot find the file specified.
Submit aborted -- fix problems then use 'p4 submit -c 1347493'.
Some file(s) could not be transferred from client.

Cause:
When you try to open a file which does not exist in perforce, it gives above error. First do a p4 add, and then open it.