Auto merge of #5678 - mdamien:patch-1, r=jdm

The urllib version used a `FancyURLOpener` which use urllib. But urllib does not not handle proxies with SSL well.

For example, when adding the proxies to urllib.FancyURLOpener, I got this SSL error:

    IOError: [Errno socket error] [Errno 1] _ssl.c:510: error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol

So I switched the function to urllib2.

A better solution would be to use `requests` but I prefer to stay with the "no-dependency" approach.

For example, this was my first solution with `requests`:

```python
def download(desc, src, dst):
    print("Downloading(R) %s..." % desc)
    with open(dst, 'wb') as handle:
        response = requests.get(src, stream=True)

        if not response.ok:
            print("something went wrong downloading %s, :(" % desc)
            sys.exit(1)

        size = int(response.headers['content-length'])
        block_size = 1024
        recved = 0
        for block in response.iter_content(1024):
            recved += len(block)
            pct = recved * 100.0 / size
            print("\rDownloading %s: %5.1f%%" % (desc, pct), end="")
            if not block:
                break
            handle.write(block)
    print()
```

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/5678)
<!-- Reviewable:end -->

0 files changed, 0 insertions, 0 deletions