nix command shouldn't print escape sequence if $TERM is set to dumb

[lufia]

Issue description

Typically, if TERM environment variable is set to dumb, then some commands should not print escape sequence such as ESC[31m, ESC[0m. nix search prints escape sequence even if set TERM=dumb.

Steps to reproduce

$ export TERM=dumb
$ nix search ansible
* ESC[0;1mnixpkgs.ESC[31;1mansibleESC[0;1mESC[0m (ESC[0;2mpython2.7-ESC[31;1mansibleESC[0;2mESC[0m)
  A simple automation tool

* ESC[0;1mnixpkgs.ESC[31;1mansibleESC[0;1m-lintESC[0m (ESC[0;2mpython2.7-
ESC[31;1mansibleESC[0;2m-lintESC[0m)
  Best practices checker for ESC[31;1mAnsibleESC[0m

Technical details

• system: "x86_64-darwin"
• host os: Darwin 18.0.0, macOS 10.14
• multi-user?: no
• sandbox: no
• version: nix-env (Nix) 2.1.3
• channels(kadota): "nixpkgs-19.03pre154968.20249caf14e"
• nixpkgs: /Users/kadota/.nix-defexpr/channels/nixpkgs

[stale[bot]]

I marked this as stale due to inactivity. → More info

[stale[bot]]

I closed this issue due to inactivity. → More info