watchtower/errors: adds pkg level errors

watchtower/errors.go

@@ -0,0 +1,18 @@
+package watchtower
+
+import "errors"
+
+var (
+	// ErrNoListeners signals that no listening ports were provided,
+	// rendering the tower unable to receive client requests.
+	ErrNoListeners = errors.New("no listening ports were specified")
+
+	// ErrNonExperimentalConf signals that an attempt to apply a
+	// non-experimental Conf to a Config was detected.
+	ErrNonExperimentalConf = errors.New("cannot use watchtower in non-" +
+		"experimental builds")
+
+	// ErrNoNetwork signals that no tor.Net is provided in the Config, which
+	// prevents resolution of listening addresses.
+	ErrNoNetwork = errors.New("no network specified, must be tor or clearnet")
+)