Unable to validate credentials: "scopes are invalid: user,repo,gist"

`flowhub init` keeps saying `Invalid username/password combination`, but it's actually catching this exception behind the scenes:

```
422 {u'message': u'Validation Failed', u'errors': [{u'field': u'scopes', u'message': u'scopes are invalid: user,repo,gist', u'code': u'custom', u'resource': u'OauthAccess'}]}
Invalid username/password combination.
```