allow light background by white <-> black

[bosr]

Hi,

Thanks for Pipenv!

When reading https://github.com/kennethreitz/pipenv/issues/545, I understood that I was one of "the 1%" ;) , well it's more the 1% who use light background terminals during the day and dark during the night (solarized).

This PR

Here is a basic way to handle light/dark backgrounds in pipenv:

• if the env variableCRAYONS_LIGHT_BG=1, then invert white and black calls (using a basic theme dict).

Yielding this

instead of this

I put the code as far as possible, close to the call site.

Alternatives

• Should this be done in colorama? Because it did not seem appropriate.
• Would you mind not distributing Crayons in the vendor folder in Pipenv, thus allowing others to deploy a crayons-light or something that does the same as the code above?

I hope this helps a bit light backgrounders, Cheers

[bosr]

Thank you for the update in pipenv 7.9.3! It works great.