pylint #21897 auto coloring of output [open]

Right now it is possible to use --output-format=colorized to get color output from pylint.

I like a lot grep --color=auto which basically uses isatty(3) to see if stdout is a tty and will in that case enable use of ansi escape codes to colorize the output. That would be a nice feature in pylint.

Default setting would be "auto" on posix systems, and "never" on windows.