Unbreak wendelin.core and pygolang tests

Hello up there.

I've noticed that wendelin.core tests became failing to build and
automatically disabled some time ago. Not good. I've tried to fix build
failures. Please see individual patches for details.

/cc @levin.zimmermann
/reviewed-by @jerome
/reviewed-on !1492
1 job for for_testrunner_1
Status Job ID Name Coverage
  External
failed ERP5.StandaloneDeploymentScriptTest-Debian.Buster.Master