Bonjour Erwan 
If you are using a localhost instance, I don't think you can use cloud_id in that case which is specific for an elasticsearch cluster running on cloud.
And I believe that localhost is the default value for this client so something like the following should work I think:
es = Elasticsearch(http_auth=('elastic', 'mypassword'))
helpers.bulk(es, some_data)
Is you local cluster secured?
If not, you can run this I think:
es = Elasticsearch()
helpers.bulk(es, some_data)