Completely replacing an old user

All,

I am trying to set up a new user for a client application, and thus want to
remove the old user afterward.

The steps are:

1/ create the new user
2/ give the new user all priviliges on database, table, sequence, function
and procedures, just like the old user
3/ deply client application with the new user and credentials
3/ Swap ownership of the databases
4/ Remove privileges from the old user
5/ Drop the old user

But I'm getting stuck on one last error message:

ERROR: role "X" cannot be dropped because some objects depend on it
DETAIL: privileges for default privileges on new functions belonging to
role postgres in schema public

The "new functions" bit is confusing. I've swapped over all the current
functions, but cannot seem to find the appropriate table for privileges on
new functions.

What am I missing here?

Regards,
Koen De Groote