Certificate signed by unknown authority

I have a custom CA cert installed on my system (which is mandatory to access internet mainly HTTPS sites). When I try to login keybase via commandline, I get the following error:

```
> keybase login
Your keybase username or email address: xxxx@xxxx.com
▶ ERROR API network error: Get https://api.keybase.io/_/api/1.0/getsalt.json?email_or_username=xxxx%40xxxx.com: x509: certificate signed by unknown authority (error 1601)
```

**Note:** The CA certificate is present in `/etc/ssl/certs/`

Reproduce the failure with `keybase login` while the custom CA is installed under `/etc/ssl/certs/`, then trace the command-line client's HTTPS certificate verification. Done means login succeeds against the Keybase API without the x509 unknown-authority error.

Written by the indexing model from the issue text.