Products.ZMySQLDA: make string_literal tolerate any strings

This reverts 8a5f5b5b (ZMySQLDA: fix string_literal usage, 2023-03-14)
to apply this logic one step lower, because CMFActivity uses
db.string_literal directly.

product/ZMySQLDA/DA.py

@@ -89,7 +89,6 @@ $Id: DA.py,v 1.4 2001/08/09 20:16:36 adustman Exp $''' % database_type
 __version__='$Revision: 1.4 $'[11:-2]
 
 import os
-import six
 from collections import defaultdict
 from weakref import WeakKeyDictionary
 import transaction
@@ -177,8 +176,6 @@ class Connection(DABase.Connection):
             # any reason, that would generate an infinite loop.
             self.connect(self.connection_string)
             connection = self._v_database_connection
-        if not isinstance(v, six.binary_type):
-            v = v.encode('utf-8')
         return connection.string_literal(v)
 
 

product/ZMySQLDA/db.py

@@ -482,9 +482,10 @@ class DB(TM):
         return items, result
 
     def string_literal(self, s):
-        # This method accepts bytes or str with only ASCII characters
-        # and return bytes.
+        try:
             return self.db.string_literal(s)
+        except UnicodeEncodeError:
+            return self.db.string_literal(s.encode('utf-8'))
 
     def _begin(self, *ignored):
         """Begin a transaction (when TM is enabled)."""