fix open encoding error.

Author: wangweichen

gitdb/db/ref.py

@@ -41,7 +41,7 @@ def _update_dbs_from_ref_file(self):
         # try to get as many as possible, don't fail if some are unavailable
         ref_paths = list()
         try:
-            with open(self._ref_file, 'r') as f:
+            with open(self._ref_file, 'r', encoding="utf-8") as f:
                 ref_paths = [l.strip() for l in f]
         except (OSError, IOError):
             pass