Add additional error handling

[johnbillion]

---

name: 🐞 Bug Fix
about: You found a bug
labels: bug

---

Description

I had difficulty figuring out the correct permissions required for the GitHub token to run this locally and I noticed that the script would error without showing the error message from the API response. This PR adds an additional error handler which is triggered if, for example, you use a GitHub token which does not have the read:org permission.

Example

> ghsvg

API failure: Your token has not been granted the required scopes to execute this query. The 'email' field requires one of the following scopes: ['user:email', 'read:user'], but your token has only been granted the: ['read:org', 'repo'] scopes. Please modify your token's scopes at: https://github.com/settings/tokens.