rest: lots of deprecation warnings in production mode logs

[audrium]

There are lots of deprecation warnings in the logs like this:

<unknown>:1: DeprecationWarning: invalid escape sequence \[

2021-11-12 16:01:59,147 | py.warnings | uWSGIWorker2Core0 | WARNING | <unknown>:1: DeprecationWarning: invalid escape sequence \[

which are repeated for almost 1.5k lines after application starts. This could be due to outdated invenio dependencies. However it's not trivial to upgrade it because we have a conflicting celery dependency (from outdated kombu version which requires celery<5.0.0 pinning).

Stems from: #417