uri = "dbname='test' host=localhost port=5432 user='user' password='password' key=gid type=POINT table="public"."test" (geom) sql="
crs_id = 4326
crs = QgsCoordinateReferenceSystem(crs_id,  QgsCoordinateReferenceSystem.EpsgCrsId)
# layer - QGIS vector layer
error = QgsVectorLayerImport.importLayer(layer, uri, "postgres", crs, False, False)
if error[0] != 0:
    iface.messageBar().pushMessage(u'Error', error[1], QgsMessageBar.CRITICAL, 5)