How to use the psycopg.IntegrityError function in psycopg

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]

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):
        self.cursor = cursor