Database error with migration
It's impossible to troubleshoot this remotely but there are a couple of things you can try to get connected to your source DB.


In your group's shared_configuration.source config you can manually add a database key with the same DB setting array properties that the migration module also looks for. For example: 


shared_configuration:
 source:
   key: database_key
    database:
      driver: mysql
      username: user
      password: pass
      ...



Use the migrate update module to template out an initial working migration config rather than manually add your source DB. For example, run: drush migrate:upgrade --legacy-db-key database_key ....