This needs to be set on portal_memcached, because it's no longer acquired since 4889d523 (Define property's default value at class level., 2012-12-31)

Use a hash to get a shorter value, because memcached keys are limited in size and a base64 of connection string was more than 70 characters.

Fix the data type for python3, this is expected to be str, not bytes.

XXX I feel setting on portal_memcached like this is wrong, I don't understand 4889d523 and it seems to me that we should revert that change now and let erp5_site_global_id be acquired from the ERP5 Site. portal_caches also uses erp5_site_global_id and it acquires it.