How to modify lookup ACL via custom REST in Python?

[GindiKhangura]

(Although this example will use Splunk's Lookup Editor app, it applies to custom REST commands in general.)

I am using the Lookup Editor provided by Splunk from SplunkBase (authored by @LukeMurphey) and am saving the lookups with the user in context, which saves it as a private user-scoped artifact.

I would like to make it globally shared while retaining the lookup's ownership information, so I attempt the following after the rest call that saves the lookup:

# Set ACL to make lookup globally shared
url = '/servicesNS/%s/%s/data/lookup-table-files/%s/acl' % (owner, namespace, lookup_file)
postargs = {
    'owner': owner, 
    'sharing': 'global'
}

rest.simpleRequest(url, postargs=postargs, sessionKey=key, raiseAllErrors=True)

When using the lookup editor as an admin, it will work fine as the admin has the capabilities to make such modifications; however, users are not able to do so and the call fails.

How can I programmatically make this REST call as an admin? I am hoping that as the script is on the server-side, I won't have to authenticate as an admin as I imagine that would require having to store credentials, which would be tricky as we have several clusters.

I have also tried making the REST call using the Splunk binary as mentioned in this Answer, but it had no effect.