image url not evaluated

david ran into an issue on commons where the extension was not able to properly
analyze a media-file url; there is no issue on the beta cluster.

the error message currently gives only the url to the media file. this patch adds
any mw http request message that may be available in order to help further
troubleshoot the issue.

also added a $wgCopyUploadProxy test to make sure the proxy option is set for the
HTTP Request when a proxy is being used.

Change-Id: Iac8d72a25b88b9a62d7b95733391a3a6103d0807
Merge "image url not evaluated"