create extension plpython3u;
ERROR:  could not load library "C:/Program Files/PostgreSQL/9.2/lib/plpython3.dll": The specified module could not be found.
--plpython3.dll есть.

CREATE EXTENSION plpython3u FROM unpackaged;
ERROR:  language "plpython3u" does not exist

SELECT * FROM pg_available_extensions WHERE name LIKE '%python%' ORDER BY name;

    name    | default_version | installed_version |                  comment                  
------------+-----------------+-------------------+-------------------------------------------
 plpython2u | 1.0             |                   | PL/Python2U untrusted procedural language
 plpython3u | 1.0             |                   | PL/Python3U untrusted procedural language
 plpythonu  | 1.0             |                   | PL/PythonU untrusted procedural language