Add requirement for TERM not to be dumb to enable colorization

[snosov1]

Hello!

This is a trivial change to disable coloring in case the terminal is dumb. Personally, I encountered the problem in Emacs terminal/compilation buffers - the coloring symbols are just printed as is (i.e. ASCII).

Technically, some more comprehensive logic can be implemented to derive color support from the TERM variable - but I'm not sure it's actually warranted. toe /usr/share/terminfo on my Ubuntu instance returns about 40 different terminal types - for some, it's clear whether the color is supported or not, for others - not that clear.

Anyway, just opting out in case of dumb terminal seems like a sensible thing to do (and it solves my problem in Emacs).

Please, let me know what you think.

[Delgan]

Hey @snosov1, thanks for your contribution! 👍

I agree with you that it seems fair to disable colors in this case. This is also what is done by supports-color.js which I sometimes use as a reference, due to the completeness of their checks.

I'm merging the PR as-is but note that I'll probably move the check to the code block right above. This is because I think the special case for $TERM="dumb" should only apply when stream is the default standard output/error. If stream happens to be a custom IOBase provided by the user, the $TERM value should become irrelevant.