RawHTTPStatusError represents any response with a 4xx or 5xx status code.

RequestError represents a generic error encountered while performing the HTTP request.

SSLValidationHostnameError replaces x509.HostnameError when the server has SSL certificate that does not match the hostname.

UnverifiedServerError replaces x509.UnknownAuthorityError when the server has SSL but the client is unable to verify it's certificate.