Google App Engine deferred.defer() failing when method returns

You should use:

result = deferred.defer(meeple_tasks.buildGames)

If you use buildGames(), that invokes the function right then and there, passing the return value to defer(). By removing the parenthesis, you pass the function itself to defer.

You need to call your deferred task like this:

deferred.defer(meeple_tasks.buildGames)

"obj must be callable" means that (in your case) the value True is not callable. How I wrote the deferred call with "defer" the buildGames method call to another process (or task) by inserting it in a queue and letting the AppEngine framework deal with it.

Note that you cannot return anything with deferred tasks. They will be running on a different process and probably on a totally different server. As per the documentation they are Background workers.