Allow to disable color in the text formatter

This commit adds support for NO_COLOR environment variable, if this is
set, colors will be disabled in the logrus text formatter.

This commit also adds support for the environment variables supported by
logrus, CLICOLOR and CLICOLOR_FORCE

Related to #1549

logging/logger.go

@@ -3,6 +3,7 @@ package logging
 import (
 	"encoding/json"
 	"net/http"
+	"os"
 	"strings"
 
 	"github.com/pkg/errors"
@@ -38,6 +39,13 @@ func New(name string, raw json.RawMessage) (*Logger, error) {
 	var formatter logrus.Formatter
 	switch strings.ToLower(config.Format) {
 	case "", "text":
+		_, noColor := os.LookupEnv("NO_COLOR")
+		// With EnvironmentOverrideColors set, logrus looks at CLICOLOR and
+		// CLICOLOR_FORCE
+		formatter = &logrus.TextFormatter{
+			DisableColors:             noColor,
+			EnvironmentOverrideColors: true,
+		}
 	case "json":
 		formatter = new(logrus.JSONFormatter)
 	case "common":