all: sync with master

internal/dhcpsvc/errors.go

@@ -1,6 +1,10 @@
 package dhcpsvc
 
-import "github.com/AdguardTeam/golibs/errors"
+import (
+	"fmt"
+
+	"github.com/AdguardTeam/golibs/errors"
+)
 
 const (
 	// errNilConfig is returned when a nil config met.
@@ -9,3 +13,9 @@ const (
 	// errNoInterfaces is returned when no interfaces found in configuration.
 	errNoInterfaces errors.Error = "no interfaces specified"
 )
+
+// newMustErr returns an error that indicates that valName must be as must
+// describes.
+func newMustErr(valName, must string, val fmt.Stringer) (err error) {
+	return fmt.Errorf("%s %s must %s", valName, val, must)
+}