display precise error while sending direct SOAP SAML message (#2614)

lemonldap-ng-portal/lib/Lemonldap/NG/Portal/Lib/SAML.pm

@@ -1864,6 +1864,9 @@ sub resolveArtifact {
             $message = $soap_answer->content();
             $self->logger->debug("Get message $message");
         }
+        else {
+            $self->logger->error("Error while sending message: ".$soap_answer->status_line);
+        }
     }
 
     return $message;