Replace "LS_COLORS" literals with a constant

pkg/cli/lscolors/lscolors.go

@@ -50,7 +50,7 @@ func GetColorist() Colorist {
 }
 
 func getLsColors() string {
-	lsColorString := os.Getenv("LS_COLORS")
+	lsColorString := os.Getenv(util.EnvLS_COLORS)
 	if len(lsColorString) == 0 {
 		return defaultLsColorString
 	}

pkg/util/util.go

@@ -6,9 +6,10 @@ package util
 // Note that some of these env vars may be significant only in special
 // circumstances; such as when running unit tests.
 const (
-	EnvHOME    = "HOME"
-	EnvPATH    = "PATH"
-	EnvPATHEXT = "PATHEXT"
-	EnvPWD     = "PWD"
-	EnvSHLVL   = "SHLVL"
+	EnvHOME      = "HOME"
+	EnvPATH      = "PATH"
+	EnvPATHEXT   = "PATHEXT"
+	EnvPWD       = "PWD"
+	EnvSHLVL     = "SHLVL"
+	EnvLS_COLORS = "LS_COLORS"
 )