Failed check if demo server is unavailable

[DDorch]

See the mail received from the CRAN team:

-------- Message transféré -------- Sujet : | CRAN package Rthingsboard -- | -- Sat, 1 Jan 2022 08:01:59 +0000 Prof Brian Ripley CRAN@R-project.org david.dorchies@inrae.fr CRAN@R-project.org

Dear maintainer,

Please see the problems shown on
<https://cran.r-project.org/web/checks/check_results_Rthingsboard.html>.

Please correct before 2022-01-15 to safely retain your package on CRAN.

It seems we need to remind you of the CRAN policy:

'Packages which use Internet resources should fail gracefully with an informative message
if the resource is not available or has changed (and not give a check warning nor error).'

This needs correction whether or not the resource recovers.

The CRAN Team