feat: add ErrNoSuchMessage to pmapi

pkg/pmapi/client.go

@@ -56,6 +56,8 @@ var (
 	ErrInvalidToken       = errors.New("refresh token invalid")
 	ErrAPINotReachable    = errors.New("cannot reach the server")
 	ErrUpgradeApplication = errors.New("application upgrade required")
+
+	ErrNoSuchMessage = errors.New("no such message")
 )
 
 type ErrUnauthorized struct {

pkg/pmapi/messages.go

@@ -532,7 +532,13 @@ func (c *Client) GetMessage(id string) (msg *Message, err error) {
 		return
 	}
 
+	if res.StatusCode == http.StatusUnprocessableEntity {
+		err = ErrNoSuchMessage
+		return
+	}
+
 	msg, err = res.Message, res.Err()
+
 	return
 }
 

pkg/pmapi/res.go

@@ -17,6 +17,8 @@
 
 package pmapi
 
+import "net/http"
+
 // Common response codes.
 const (
 	CodeOk = 1000