Restore some code from original version which has been removed accidentally by someone.

src/zc/buildout/download.py

@@ -180,8 +180,6 @@ class Download(object):
         self.logger.info('Downloading %s' % url)
         urllib._urlopener = url_opener
         handle, tmp_path = tempfile.mkstemp(prefix='buildout-')
-
-        try:
         try:
             if not download_network_cached(self.network_cache, tmp_path,
                                                         url, self.logger):
@@ -194,11 +192,15 @@ class Download(object):
                 # Upload the file to networkcached.
                 upload_network_cached(self.network_cache, url,
                                                      tmp_path, self.logger)
-            finally:
-                os.close(handle)
-        except:
+        except IOError, e:
+            os.remove(tmp_path)
+            raise zc.buildout.UserError("Error downloading extends for URL "
+                              "%s: %r" % (url, e[1:3]))
+        except Exception, e:
             os.remove(tmp_path)
             raise
+        finally:
+            os.close(handle)
 
         if path:
             shutil.move(tmp_path, path)