Add a print_message() or similar function in admin CLI

[govint]

With each change that goes in for the admin CLI there is a chance that Python 3.5 incompatible changes get checked in - especially try - except blocks (uses except (exception name), e:) and print statements.

There are multiple places where new print messages keep getting added and those break the admin CLI on VSphere 6.5 (Python 3.5).

Instead define a new print_message() function that is called everywhere in the CLI code and it in turn uses the correct syntax for printing.

[govint]

Closing, may be just rely on using a coding guideline to be Python 3.5 compliant when making changes.