add ldv_migrate script

ldv_migrate/ldv_migrate/connection/retrieve_db_connection.py

 import sys
 
 import psycopg2
+try:
     from connection.config import read_config
+except:
+    from ldv_migrate.connection.config import read_config
+
 import logging
 import argparse
 from sshtunnel import SSHTunnelForwarder