Error due to GitHub rate limit

[craigrodway]

After installing this module on a hosted ProcessWire 2.4.1 site, the Setup > Upgrade page was blank.

Enabling $config->debug then showed this message at the top of the page:

Warning: Illegal string offset 'name' in /[...]/site/modules/ProcessWireUpgrade/ProcessWireUpgradeCheck.module on line 273

The $data variable holds this array:

Array
(
    [message] => API rate limit exceeded for 91.208.99.2. (But here's the good news: Authenticated requests get a higher rate limit. Check out the documentation for more details.)
    [documentation_url] => https://developer.github.com/v3/#rate-limiting
)

It just seems to be that this situation is not handled in a way that produces a meaningful error. Incidentally, $http->getError() doesn't seem to be helpful either.