How to resolve error 'migration_group' entity with ID 'migrate_drupal_7' already exists? I have been trying to migrate to Drupal 8 using the drush. I have followed all the instruction as mentioned in [https://drupalize.me/blog/201604/custom-drupal-drupal-migrations-migrate-tools][1]

After installation, enabled all the required modules like migrate upgrade, migrate tools and migrate plus, and then added the code in settings.php file mentioned below.

 // Database entry for `drush migrate-upgrade --configure-only`
$databases['upgrade']['default'] = array (
  'database' =&gt; 'dbname',
  'username' =&gt; 'dbuser',
  'password' =&gt; 'dbpass',
  'prefix' =&gt; '',
  'host' =&gt; 'localhost',
  'port' =&gt; '3306',
  'namespace' =&gt; 'Drupal\\Core\\Database\\Driver\\mysql',
  'driver' =&gt; 'mysql',
);
// Database entry for `drush migrate-import --all`
$databases['migrate']['default'] = array (
  'database' =&gt; 'dbname',
  'username' =&gt; 'dbuser',
  'password' =&gt; 'dbpass',
  'prefix' =&gt; '',
  'host' =&gt; 'localhost',
  'port' =&gt; '3306',
  'namespace' =&gt; 'Drupal\\Core\\Database\\Driver\\mysql',
  'driver' =&gt; 'mysql',
);


Now used the command - **drush migrate-upgrade --configure-only --legacy-db-url=mysql://dbuser:dbpass@localhost/dbname --legacy-root=/path/to/sites/default/files** and than drush returns the following errors - ***'migration_group' entity with ID 'migrate_drupal_7' already exists*** 

How can I resolve the error?
you can delete existing migration groups from: /admin/structure/migrate