I'm a little puzzled by both the problem and the error.
In my 7.3.1 environment when I look at the prpcUtils.sh script the line which is trying to source the posixUtils.sh file is on line 41. Whereas the error message that you're seeing seems to suggest it's from line 45.
Have you made any modifications to the script? Also is this from the full media or the Update only media?
The prpcUtils.sh should be under /scripts/utils
And posixUtils.sh is under /scripts
Do you mean you don't have this file at all? Or you do have a file but it's empty?