Deprecate --egg

[dstufft]

Fixes #1749
Fixes #1320
Closes #3711

[sigmavirus24]

[pfmoore]

@dstufft - any idea why this didn't get checked with appveyor? It's no different to #3950 as far as I can see, but that one has both travis and appveyor checks (with only travis being required) and this one only has travis :-(

[dstufft]

@pfmoore Um, I don't know. Looking at the logs Appveyor returned an error:

Cache-Control: no-cache
Content-Length: 48
Content-Type: application/json; charset=utf-8
Date: Wed, 07 Sep 2016 14:40:37 GMT
Expires: -1
Pragma: no-cache
Server: Microsoft-IIS/8.5
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET

{"message":"Pull request #3956 does not exist."}

Except I don't know why it returned a 404. This PR obviously does exist.

[dstufft]

To be clear, the reason it doesn't list Appveyor at all is because Appveyor never reported a status. Once you mark a service as required then Github will automatically add a pending status to every PR for that, but for non required services it waits until the service reports a status.

[pfmoore]

OK, weird. I'll ping appveyor about it. Thanks.

[pfmoore]

Redelivering the webhook request seems to have fixed it - looks like it was just some sort of intermittent glitch.

[mithrandi]

Occasionally it seems GitHub delivers webhooks for new PRs before the PR object is fully visible in the API; I've seen inconsistencies like this before (maybe some caching / eventual consistency issue?).