Cryptic error message if GitHub token is incorrect

If you have leading/trailing space in token in config.toml (error in copy-pasting) i.e.
```
[github]
token = " TOKEN_HERE"
```
gitout
- will be able to get repositories information including private ones
- will crash when trying to clone first private repository it tries with cryptic error:
```
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Error { code: -1, klass: 34, message: "too many redirects or authentication replays" }', src/libcore/result.rs:1188:5
```

If token is incorrect in the other way then `gitout` crashes when trying to get repos info with
```
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /usr/src/rustc-1.41.0/src/libcore/macros/mod.rs:15:40
```

More helpful error message would be appreciated.
My api token is 40 hex characters.
I am not sure whether one could assert token format as there are probably no long-term guarantees in GitHub API.
I would assume there should be some endpoint which allows for easy checking whether provided token is correct. I checked that https://stackoverflow.com/a/58572011 seems to ignore extra spaces, haven't tried GraphQL API.

Start by tracing how the token from config.toml is used when fetching repository information and cloning private repositories. Reproduce both invalid-token cases, then replace the cryptic unwrap failures with helpful authentication errors; done means incorrect or whitespace-padded tokens fail without a panic.

Written by the indexing model from the issue text.