This introduces reviewboard.cmdline.utils.console.Console, which is a

new interface for outputting to the console. It takes care of wrapping

text to terminal widths, styling some content, and has functions for

outputting standard pieces of content to the console (such as

paragraphs, notes, warnings, errors, lists of items, and progress

steps).
This is the successor to the old ConsoleUI, built to be more generic

and usable outside of a wizard setup. ConsoleUI still exists, but now

wraps this and will be phased out, since the multi-UI support hasn't

been needed in a long time, and much of its remaining page-based design

is no longer relevant.
The new Console interface will be used for some parts of rbext and

for other command line helpers in the future.
Some styling has improved. The default terminal width is now wider at 79

characters. Itemized lists are no longer indented too far, and their

items now wrap correctly. Errors are no longer treated specially with

regards to their prefix vs. text placement (previously, we indented all

text to align with the placement of error text, after the [!] prefix).

These changes should help keep console output a bit more consistent.
Otherwise, rb-site and prepare-dev.py both appear more or less the

same as they did before.

Tested all of rb-site and prepare-dev.py with Python 2.7, 3.6, and

3.9, at different terminal widths. Verified the results looked the way

I wanted.