Unable to login on command-line

I created a new Keybase account, let Keybase generate a key for me, then exported it. Now I get:

```
keybase login
error: `gpg` exited with code 2
warn: gpg: [don't know]: invalid packet (ctb=2d)
warn: gpg: keydb_search_first failed: invalid packet
```

Start by reproducing `keybase login` with the newly created and exported key, then inspect the reported `gpg` exit code and invalid-packet warnings. Compare the login path with the key-generation and export steps described in the report; done means identifying and resolving the cause so command-line login succeeds.

Written by the indexing model from the issue text.