Fixed #19152 -- Allowed PostGIS tests to be run without template

from django.conf import settings

from django.core.exceptions import ImproperlyConfigured

from django.db.backends.postgresql_psycopg2.creation import DatabaseCreation

from django.utils.functional import cached_property

class PostGISCreation(DatabaseCreation):

    geom_index_type = 'GIST'

    geom_index_ops = 'GIST_GEOMETRY_OPS'

    geom_index_ops_nd = 'GIST_GEOMETRY_OPS_ND'

    @cached_property

    def template_postgis(self):

        template_postgis = getattr(settings, 'POSTGIS_TEMPLATE', 'template_postgis')

        cursor = self.connection.cursor()

        cursor.execute('SELECT 1 FROM pg_database WHERE datname = %s LIMIT 1;', (template_postgis,))

        if cursor.fetchone():

            return template_postgis

        return None

    def sql_indexes_for_field(self, model, f, style):

        "Return any spatial index creation SQL for the field."

        from django.contrib.gis.db.models.fields import GeometryField

        return output

    def sql_table_creation_suffix(self):

        postgis_template = getattr(settings, 'POSTGIS_TEMPLATE', 'template_postgis')

        return ' TEMPLATE %s' % self.connection.ops.quote_name(postgis_template)

        if self.template_postgis is not None:

            return ' TEMPLATE %s' % (

                self.connection.ops.quote_name(self.template_postgis),)

        return ''

    def _create_test_db(self, verbosity, autoclobber):

        test_database_name = super(PostGISCreation, self)._create_test_db(verbosity, autoclobber)

        if self.template_postgis is None:

            # Connect to the test database in order to create the postgis extension

            self.connection.close()

            self.connection.settings_dict["NAME"] = test_database_name

            cursor = self.connection.cursor()

            cursor.execute("CREATE EXTENSION postgis")

            cursor.commit()

        return test_database_name