Update documentation to reflect JSON import behavior

The docs don't need to describe what will happen on Python versions
before 2.6 as they are unsupported by psycopg2.

Should have been included in commit
d58844e548, but was missed.

doc/src/extras.rst

@@ -539,17 +539,13 @@ fields to JSON) you can use the `register_json()` function.
 
 .. __: http://people.planetpostgresql.org/andrew/index.php?/archives/255-JSON-for-PG-9.2-...-and-now-for-9.1!.html
 
-The Python library used by default to convert Python objects to JSON and to
-parse data from the database depends on the language version: with Python 2.6
-and following the :py:mod:`json` module from the standard library is used;
-with previous versions the `simplejson`_ module is used if available. Note
-that the last `!simplejson` version supporting Python 2.4 is the 2.0.9.
+The Python :py:mod:`json` module is used by default to convert Python objects
+to JSON and to parse data from the database.
 
 .. _JSON: http://www.json.org/
 .. |pgjson| replace:: :sql:`json`
 .. |jsonb| replace:: :sql:`jsonb`
 .. _pgjson: http://www.postgresql.org/docs/current/static/datatype-json.html
-.. _simplejson: http://pypi.python.org/pypi/simplejson/
 
 In order to pass a Python object to the database as query argument you can use
 the `Json` adapter::

lib/_json.py

@@ -50,9 +50,7 @@ class Json(object):
 
     `!Json` can be used to wrap any object supported by the provided *dumps*
     function. If none is provided, the standard :py:func:`json.dumps()` is
-    used (`!simplejson` for Python < 2.6;
-    `~psycopg2.extensions.ISQLQuote.getquoted()` will raise `!ImportError` if
-    the module is not available).
+    used.
 
     """
     def __init__(self, adapted, dumps=None):