Calling a python module from postgres function

gistfile1.sql

CREATE FUNCTION pymax (a integer, b integer)
  RETURNS integer
AS $$
  if a > b:
    return a
  return b
$$ LANGUAGE plpythonu;

SELECT pymax(1,2) #=> 2

CREATE TYPE google_lon_lat AS (lon numeric, lat numeric);

CREATE FUNCTION google_geocode(param_address text) RETURNS
     google_lon_lat
AS
$$
 from googlemaps import GoogleMaps
 gmaps = GoogleMaps()
 arg_lat, arg_long = gmaps.address_to_latlng(param_address)
 return (arg_long, arg_lat)
$$
language 'plpythonu';

SELECT google_geocode('2 Birkenhead Ave, Wantirna, VIC, 3152')

ERROR:  ImportError: No module named googlemaps
CONTEXT:  Traceback (most recent call last):
  PL/Python function "google_geocode", line 2, in <module>
    from googlemaps import GoogleMaps
PL/Python function "google_geocode"


********** Error **********

ERROR: ImportError: No module named googlemaps
SQL state: XX000
Context: Traceback (most recent call last):
  PL/Python function "google_geocode", line 2, in <module>
    from googlemaps import GoogleMaps
PL/Python function "google_geocode"

https://gist.github.com/oginga/da29a1a99527dff59cf61ec687a5c963