Fix sniffing composite files to reuse existing abstractions.

tools/data_source/upload.py

@@ -11,8 +11,6 @@
 import sys
 from json import dump, load, loads
 
-from six.moves.urllib.request import urlopen
-
 from galaxy.datatypes import sniff
 from galaxy.datatypes.registry import Registry
 from galaxy.datatypes.upload_util import handle_upload, UploadProblemException
@@ -184,7 +182,7 @@ def to_path(path_or_url):
         is_url = path_or_url.find('://') != -1  # todo fixme
         if is_url:
             try:
-                temp_name = sniff.stream_to_file(urlopen(path_or_url), prefix='url_paste')
+                temp_name = sniff.stream_url_to_file(path_or_url)
             except Exception as e:
                 raise UploadProblemException('Unable to fetch %s\n%s' % (path_or_url, unicodify(e)))