Detect STDOUT isn't a TTY and disable color

CHANGELOG.md

@@ -10,6 +10,7 @@ IMPROVEMENTS:
    rolling update could remove an unnecessary amount of allocations [GH-3070]
  * api: Redact Vault.Token from AgentSelf response [GH-2988]
  * cli: node-status displays node version [GH-3002]
+ * cli: Disable color output when STDOUT is not a TTY [GH-3057]
  * client: Unmount task directories when alloc is terminal [GH-3006]
  * client/template: Allow template to set Vault grace [GH-2947]
  * client/template: Template emits events explaining why it is blocked [GH-3001]

command/meta.go

@@ -10,6 +10,7 @@ import (
 	"github.com/hashicorp/nomad/api"
 	"github.com/mitchellh/cli"
 	"github.com/mitchellh/colorstring"
+	"golang.org/x/crypto/ssh/terminal"
 )
 
 const (
@@ -126,7 +127,7 @@ func (m *Meta) Client() (*api.Client, error) {
 func (m *Meta) Colorize() *colorstring.Colorize {
 	return &colorstring.Colorize{
 		Colors:  colorstring.DefaultColors,
-		Disable: m.noColor,
+		Disable: m.noColor || !terminal.IsTerminal(int(os.Stdout.Fd())),
 		Reset:   true,
 	}
 }