Fix most of the bsddb3 tests.
diff --git a/Lib/bsddb/dbtables.py b/Lib/bsddb/dbtables.py
index 690e280..fda1273 100644
--- a/Lib/bsddb/dbtables.py
+++ b/Lib/bsddb/dbtables.py
@@ -90,8 +90,8 @@
 #
 # keys used to store database metadata
 #
-_table_names_key = '__TABLE_NAMES__'  # list of the tables in this db
-_columns = '._COLUMNS__'  # table_name+this key contains a list of columns
+_table_names_key = b'__TABLE_NAMES__'  # list of the tables in this db
+_columns = b'._COLUMNS__'  # table_name+this key contains a list of columns
 
 def _columns_key(table):
     return table + _columns