PropEr tests sometimes fails with `cant_generate`

[jesperes]

Sometimes the PropEr will fail with cant_generate: https://github.com/klarna-incubator/bec/actions/runs/3088243798/jobs/4994492361#step:7:106. This needs to be investigated.

[jesperes]

Console output:

===> Testing prop_api:prop_api()
Workzone plugin is not supported. Corresponding tests will not be run.
Hook 'com.nerdwin15.stash-stash-webhook-jenkins:jenkinsPostReceiveHook' is not available and will not be tested.
Hook 'de.aeffle.stash.plugin.stash-http-get-post-receive-hook:http-get-post-receive-hook' is not available and will not be tested.
....................................................................................................
OK: Passed 100 test(s).

11% {prop_api,set_groups,3}
10% {prop_api,set_public,3}
9% {prop_api,set_enabled_hooks,3}
9% {prop_api,set_branch_restrictions,3}
9% {prop_api,set_users,3}
9% {prop_api,set_default_branch,3}
6% {prop_api,set_webhooks,3}
5% {prop_api,get_default_branch,2}
5% {prop_api,get_public,2}
5% {prop_api,get_users,2}
4% {prop_api,get_groups,2}
4% {prop_api,get_branch_restrictions,2}
3% {prop_api,get_webhooks,2}
3% {prop_api,get_enabled_hooks,2}
===> 
1/2 properties passed, 1 failed
===> Failed test cases:
prop_yml:prop_yml() -> {error,cant_generate}
Error: Process completed with exit code 1.