How to use the psycopg.DatabaseError function in psycopg

from django.db.backends import *
from django.db.backends.signals import connection_created
from django.db.backends.postgresql.client import DatabaseClient
from django.db.backends.postgresql.creation import DatabaseCreation
from django.db.backends.postgresql.introspection import DatabaseIntrospection
from django.db.backends.postgresql.operations import DatabaseOperations
from django.db.backends.postgresql.version import get_version
from django.utils.encoding import smart_str, smart_unicode

try:
    import psycopg as Database
except ImportError, e:
    from django.core.exceptions import ImproperlyConfigured
    raise ImproperlyConfigured("Error loading psycopg module: %s" % e)

DatabaseError = Database.DatabaseError
IntegrityError = Database.IntegrityError

class UnicodeCursorWrapper(object):
    """
    A thin wrapper around psycopg cursors that allows them to accept Unicode
    strings as params.

    This is necessary because psycopg doesn't apply any DB quoting to
    parameters that are Unicode strings. If a param is Unicode, this will
    convert it to a bytestring using database client's encoding before passing
    it to psycopg.

    All results retrieved from the database are converted into Unicode strings
    before being returned to the caller.
    """
    def __init__(self, cursor, charset):

def execute(self, sql, params=()):
        try:
            return self.cursor.execute(smart_str(sql, self.charset), self.format_params(params))
        except Database.IntegrityError, e:
            raise utils.IntegrityError, utils.IntegrityError(*tuple(e)), sys.exc_info()[2]
        except Database.DatabaseError, e:
            raise utils.DatabaseError, utils.DatabaseError(*tuple(e)), sys.exc_info()[2]

import sys, string, os.path, fileinput, os, time, getpass, glob, re

# 3rd party imports
dbapi = None
try:
	from pyPgSQL import PgSQL
	from pyPgSQL import libpq
	dbapi = PgSQL
	db_error = libpq.DatabaseError
	dsn_format = "%s:%s:%s:%s:%s"
except ImportError:
	_log.LogException("Cannot load pyPgSQL.PgSQL database adapter module.", sys.exc_info(), verbose=0)
	try:
		import psycopg
		dbapi = psycopg
		db_error = psycopg.DatabaseError
		dsn_format = "host=%s port=%s dbname=%s user=%s password=%s"
	except ImportError:
		_log.LogException("Cannot load psycopg database adapter module.", sys.exc_info(), verbose=0)
		try:
			import pgdb
			dbapi = pgdb
			db_error = pgdb.DatabaseError
			dsn_format = "%s:%s:%s:%s:%s"
		except ImportError:
			print "Cannot find Python module for connecting to the database server. Program halted."
			print "Please check the log file and report to the mailing list."
			_log.LogException("Cannot load pgdb database adapter module.", sys.exc_info(), verbose=0)
			raise

# GnuMed imports
try:

"""
PostgreSQL database backend for Django.

Requires psycopg 1: http://initd.org/projects/psycopg1
"""

from django.core.db import base, typecasts
import psycopg as Database

DatabaseError = Database.DatabaseError

try:
    # Only exists in python 2.4+
    from threading import local
except ImportError:
    # Import copy of _thread_local.py from python 2.4
    from django.utils._threading_local import local

class DatabaseWrapper(local):
    def __init__(self):
        self.connection = None
        self.queries = []

    def cursor(self):
        from django.conf.settings import DATABASE_USER, DATABASE_NAME, DATABASE_HOST, DATABASE_PORT, DATABASE_PASSWORD, DEBUG, TIME_ZONE
        if self.connection is None: