Validation module is broken with remote CardDav

summary

When trying to add a new address book with a remote dav server (nextcloud 15), I cannot pass the validation process (user/password/URL)

screenshot

Untitled

steps to reproduce the bug

  1. Create a new remote carddav address book
  2. Try to validate URL + username + password

current behavior

Validation failed (tried on my phone, everything is working fine)

expected behavior

Validation succeed

my version numbers

  • CardBook: 34.1
  • Thunderbird: 60.0.4
  • OS: Debian Stretch/Buster

CardBook log

2019.02.08 00:30:22:943 : Validation module : Validating without discovery request on https://XXXXXXXXXX/remote.php/dav/addressbooks/users/XXXXXXXXXX/contacts/ …
2019.02.08 00:30:22:992 : Validation module : Synchronization failed (step : validateWithoutDiscovery, url : https://XXXXXXXXXX/remote.php/dav/addressbooks/users/XXXXXXXXXX/contacts/, status : 503)
2019.02.08 00:30:23:958 : Validation module : Discovering phase 1 request on https://XXXXXXXXXX/remote.php/dav/addressbooks/users/XXXXXXXXXX/contacts/.well-known/carddav …
2019.02.08 00:30:24:008 : Validation module : Synchronization failed (step : discoverPhase1, url : https://XXXXXXXXXX/remote.php/dav/addressbooks/users/XXXXXXXXXX/contacts/.well-known/carddav, status : 503)
2019.02.08 00:30:24:973 : Validation module : Validating without discovery request on https://XXXXXXXXXX/remote.php/dav/addressbooks/XXXXXXXXXX …
2019.02.08 00:30:25:023 : Validation module : Synchronization failed (step : validateWithoutDiscovery, url : https://XXXXXXXXXX/remote.php/dav/addressbooks/XXXXXXXXXX, status : 503)