Add fetch errors

[RickBarretto]

https://github.com/RickBarretto/pre-audit/blob/df96c30e1e5467ffdea573b53d50b798a996d178/src/core/fetch_api.py

Needs to handle http errors and handle "dependency not found".

Cause: when the package isn't in database, it returns this error:

return [(report["id"], report["details"]) for report in self.reports]
TypeError: 'NoneType' object is not iterable

[RickBarretto]

Closed by #2