upload command supports python3

slapcache/signature.py

@@ -87,7 +87,7 @@ class NetworkCache:
     else:
       key = self.directory_key
 
-    file_descriptor = open(path, 'r')
+    file_descriptor = open(path, 'rb')
     if not (self.dir_url and self.cache_url):
       raise ValueError("upload-dir-url and/or upload-cache-url is not defined")