keybase-installer cannot update client when private key is not stored in Keybase

I tried updating my Keybase client today, as I am currently running 0.7.7. However, when I go to update my software, I receive the exit codes 2 and 254.

```
$ sudo keybase update
warn: No config file found; tried '/root/.config/keybase/config.json'
info: Computed npm install prefix: /
info: Found keybase-installer: keybase-installer v1.0.0
info: Detected custom path '/.'; preserving it!
info: Attempting software upgrade.....
info: Running `keybase-installer -g gpg2 --prefix /.`
info: Made temporary directory: /tmp/keybase_install_aBW6rS7IBK_bsf0EU2sPmw
info: Using keyset version v1
info: Fetching URL https://dist.keybase.io/sig/files/1/index.asc
info: cleaning up tmpdir /tmp/keybase_install_aBW6rS7IBK_bsf0EU2sPmw
error: exit code 2
warn: gpg: key 7F9E8BFA: public key "Keybase.io Index Signing (v1) " imported
warn: gpg: failed to create temporary file '/root/.gnupg/.#lk0x0000000001036ec0.justin-w-florys-desktop.7697': No such file or directory
warn: gpg: can't connect to the agent: No such file or directory
warn: gpg: Total number processed: 1
warn: gpg: imported: 1
warn: gpg: no ultimately trusted keys found
error: exit code 254
```

It seems that when running this under root privileges, it cannot detect my local cached private key to successfully update Keybase? I'm unsure what to make of this.

For testing purposes, I tried copying my `config.json` file from my user directory to the root directory `/root/.config/keybase/config.json`, but all this did was eliminate the exit code 254. I still ran into exit code 2 and the update process failed.

Is there any way to update Keybase without storing your private key in the cloud?

Start by reproducing `sudo keybase update` with the reported `keybase-installer -g gpg2 --prefix /.` path and inspect how the installer uses `/root/.config/keybase/config.json` and GnuPG temporary files. Compare behavior with the user's configuration and permissions; done means updates succeed without requiring the private key to be stored remotely.

Written by the indexing model from the issue text.