Django tests don't find the postgres extensions

I am running python tests like this.

python manage.py test

.....
[snip]
.....

LINE 1: SELECT (idx([snip])...
                ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.

I am on ubuntu, with postgres 9.1, and Django 1.5.x, I am also using nose.

So my tests can't find the idx function.

I have installed the intarray extension, which has the idx functions. I can verify it by:

psql (9.1.10)
Type "help" for help.

postgres=# use template1
postgres-# \dx
                                     List of installed extensions
   Name   | Version |   Schema   |                            Description                             
----------+---------+------------+--------------------------------------------------------------------
 hstore   | 1.0     | public     | data type for storing sets of (key, value) pairs
 intarray | 1.0     | public     | functions, operators, and index support for 1-D arrays of integers
 plpgsql  | 1.0     | pg_catalog | PL/pgSQL procedural language
(3 rows)

postgres-# use template_postgis;
ERROR:  syntax error at or near "use"
LINE 1: use template1
        ^
postgres=# use template_postgis
postgres-# \dx
                                     List of installed extensions
   Name   | Version |   Schema   |                            Description                             
----------+---------+------------+--------------------------------------------------------------------
 hstore   | 1.0     | public     | data type for storing sets of (key, value) pairs
 intarray | 1.0     | public     | functions, operators, and index support for 1-D arrays of integers
 plpgsql  | 1.0     | pg_catalog | PL/pgSQL procedural language
(3 rows)

postgres-# 

This code runs correctly with my dev environment. (Using the same postgres install, but which also has intarray).

It looks this issue was solved in:

Installing hstore extension in django nose tests

But I have tried the steps in that question with no help.