Fix error message formatting

Author: behackett

pymongo/pool.py

@@ -431,7 +431,7 @@ def send_message(self, message, max_doc_size):
  if (self.max_bson_size is not None
  and max_doc_size > self.max_bson_size):
  raise DocumentTooLarge(
- "BSON document too large (%d bytes) - the connected server"
+ "BSON document too large (%d bytes) - the connected server "
  "supports BSON document sizes up to %d bytes." %
  (max_doc_size, self.max_bson_size))