Cannot update keybase, "Access Denied" to prerelease.keybase.io / Tor

Unable to update Keybase. I would guess you are blocking Tor? Is that really necessary? I think not.
```
Err http://prerelease.keybase.io/deb/ stable/main keybase amd64 2.5.0-20180802173336.f9c762fe53
403 Forbidden [IP: 143.204.29.81 80]
E: Failed to fetch http://prerelease.keybase.io/deb/pool/main/k/keybase/keybase_2.5.0-20180802173336.f9c762fe53_amd64.deb 403 Forbidden [IP: 143.204.29.81 80]
```

And when visiting the URL in a browser, the following is returned,
`AccessDeniedAccess Denied6705E4FA5BDF31C0MRUr40qDBtr6JNvKLJCgwur887+RMa8QgqkBVBKFEyVqvxZLJkjRCI0/YIxBEH2MIuR3lZyJgbs=`

Start by reproducing the package fetch from prerelease.keybase.io using the reported Debian URL and checking the returned 403 AccessDenied response. Trace the release or package-distribution configuration responsible for that endpoint, if it is present in this repository. Done means the affected package can be fetched successfully through the reported update path, including from the described network.

Written by the indexing model from the issue text.