Handle Authentication error

Log example:

09-01 14:13:57:367 [ info nextcloud.sync.accessmanager ]:	2 "" "https://nextcloud.inrae.fr/ocs/v1.php/cloud/capabilities?format=json" has X-Request-ID "7e182d3c-9bd4-4576-88a3-6fa69febf9a2"
09-01 14:13:57:373 [ info nextcloud.sync.networkjob ]:	OCC::JsonApiJob created for "https://nextcloud.inrae.fr" + "ocs/v1.php/cloud/capabilities" ""
09-01 14:13:57:856 [ warning nextcloud.sync.credentials.http ]:	Stop request: Authentication failed for  "https://nextcloud.inrae.fr/ocs/v1.php/cloud/capabilities?format=json"
09-01 14:13:57:856 [ warning nextcloud.sync.networkjob ]:	QNetworkReply::AuthenticationRequiredError "Host requires authentication" QVariant(int, 401)
09-01 14:13:57:856 [ info nextcloud.sync.networkjob.jsonapi ]:	JsonApiJob of QUrl("https://nextcloud.inrae.fr/ocs/v1.php/cloud/capabilities?format=json") FINISHED WITH STATUS "AuthenticationRequiredError Host requires authentication"
09-01 14:13:57:856 [ warning nextcloud.sync.networkjob.jsonapi ]:	Network error:  "ocs/v1.php/cloud/capabilities" "Host requires authentication" QVariant(int, 401)
09-01 14:13:57:856 [ debug default ]	[ main::::operator() ]:	Server capabilities QJsonObject()