Broken images all the time in Github readme

[g105b]

I've been in touch with Github over the time period of about 4 months regarding this issue.

In short, I can always successfully visit the URL to the Shields image, but when it is proxied by Github's githubusercontent.com domain, Shields images often appear broken.

For an example, head over to https://github.com/PhpGt/Dom and keep refreshing. For me, one in every ten requests ends up looking something like this:

Which images are broken is different each time.

Here is a screenshot of my network tab in Chrome Developer Tools for one of the broken images:

I'm not sure what to suggest, but Github have clearly stated that it is not their problem, it is the problem of the remote image server. Happy to help with whatever details you need from me.

[g105b]

Another example website I have noticed the same issue on:

[g105b]

Response from Github staff when I complained about this issue to them:

From: Antonio Diaz (Github Staff)
To: Greg Bowler

Hey Greg,

Thanks for your patience as we investigated this. Looking in our logs, connections to the site
that hosts your badge images, sometimes fail. This does not appear to be a problem with our image
proxy.

If you're seeing broken images from that site, I would recommend reaching out to them to see what
might be causing these unreliable connections.

Cheers,
Antonio

[MarkVaughn]

also getting this from all over our projects e.g
https://github.com/paratestphp/paratest

very common badges (travis, scrutinizer, packagist)

[![Build Status](https://travis-ci.org/paratestphp/paratest.svg?branch=master)](https://travis-ci.org/paratestphp/paratest)
[![Code Coverage](https://scrutinizer-ci.com/g/brianium/paratest/badges/coverage.png?b=master)](https://scrutinizer-ci.com/g/brianium/paratest/?branch=master)
[![Scrutinizer Code Quality](https://scrutinizer-ci.com/g/brianium/paratest/badges/quality-score.png?b=master)](https://scrutinizer-ci.com/g/brianium/paratest/?branch=master)
[![Packagist](https://img.shields.io/packagist/dt/brianium/paratest.svg)](https://packagist.org/packages/brianium/paratest)

[paulmelnikow]

Hi, thanks for the report. The issue is caused by slow responses from the Shields server combined with GitHub's image proxy's timeout. (The combination causes slow images to be rendered as missing images.)

This is a duplicate of #1568. Let's discuss there.