Related to #169. Reported in Azure/azure-cli#6080. Also caused side effect of Azure/azure-cli#9903.

If stdout is redirected and CLI displays a colored error message, the color in the console can't revert back to the default which is caused by tartley/colorama#200.

Without proper a fix from Colorama, Knack should have the ability to disable color. This can be done by extending _should_enable_color by supporting env var like KNACK_ENABLE_COLOR or KNACK_DISABLE_COLOR.