Adding HTTP status code to FileTransferError

[Don Coleman]

I'd like to add HTTP Status Code and HTTP Status Message to FileTransferError.

Any objections?

{
       "code": FILE_NOT_FOUND_ERR
       "source": "http://example.com/missing.txt";,
       "target": "file:///mnt/sdcard/foo.txt",
       "http_status": 404
       "http_message": "Not Found"
}

{
       "code": CONNECTION_ERR
       "source": "http://example.com/protected.txt";,
       "target": "file:///mnt/sdcard/bar.txt",
       "http_status": 401
       "http_message": "Authorization Required"
}

{
       "code": CONNECTION_ERR
       "source": "http://example.com/admin.txt";,
       "target": "file:///mnt/sdcard/baz.txt",
       "http_status": 403
       "http_message": "Forbidden"
}