Fix bug #422702: Make flag argument to open optional, and document it that way.
diff --git a/Lib/dbhash.py b/Lib/dbhash.py
index ad94ed8..7aec772 100644
--- a/Lib/dbhash.py
+++ b/Lib/dbhash.py
@@ -12,5 +12,5 @@
 
 error = bsddb.error                     # Exported for anydbm
 
-def open(file, flag, mode=0666):
+def open(file, flag = 'r', mode=0666):
     return bsddb.hashopen(file, flag, mode)