Fix passed parameters.

src/zc/buildout/testing.py

@@ -303,9 +303,7 @@ def get_filename_from_upload_network_cached(**kw):
   import json
   logger = logging.getLogger('zc.buildout')
   nc_server_path = kw.pop('nc_server_path')
-  default_params = dict(logger=logger,
-                        signature_certificate_file='',
-                        signature_private_key_file=None)
+  default_params = dict(logger=logger, signature_private_key_file=None)
   kw.update(default_params)
   if not zc.buildout.networkcache.upload_network_cached(**kw):
     return 'Upload failed.'