var brokenJson = function (url) {
    var responseCopy;
    return fetch(url)
    .then(function (response) {
        responseCopy = response.clone();
        return response.json();
    }).catch(function (err) {
        if (err instanceof SyntaxError) {
            return responseCopy.text()
            .then(function(text) {
                console.error(text);
                throw err;
            });
        }
        else {
            throw err;
        }
    }).then(function (json) {
        // do things
    });
};