Error: signature verification failed

Whenever I try to use the `prove` subcommand, I get:

```
user@host: keybase prove github
error: flamsmark: signature verification failed
```

The error message is red, and bold, which is exciting, but I don't see any logs or other useful adjuncts to debug the problem.

No files or tests are named. Start by reproducing `keybase prove github` and investigate how the `prove` subcommand reports `flamsmark: signature verification failed`; done means the failure provides logs or other useful debugging details.

Written by the indexing model from the issue text.