internal service user lose its acl after upgrade

We are unable to reproduce the bug, but here the info/bug/symptom

Given wazo-19.15
When I upgrade to wazo-19.16
Then I have the following error:

The complete error from wazo-auth is:

This error causes the suppression of all policy's ACL

What we have done to reproduce:

• Take a backup from the wazo on which the error occurs just before the upgrade

• restore the backup on docker environment with an up-to-date wazo-auth.

• Execute database migration scripts (to simulate what the upgrade does)

• run wazo-auth-keys service update (i.e. the failing script 20-wazo-update-keys.sh)
  But everything goes well ...
  There is also nothing in the code that can explain this behavior

We also run wazo-auth-keys service update in a loop during 30 minutes, but nothing

We have found some things that can mitigate this behavior, like do not remove all ACL if something goes wrong, but only to set it to the old ACL. We also think that refactoring this piece of code can eliminate this problem too (but we have nothing to prove it).

So this ticket will be considered close when the refactor is done and check if the problem comes back on other wazo