title: Cannot set destination table with BigQuery Python API
body: <p>I'm recently getting the following BigQuery error when using the Python API:</p>
  
  <p><strong>google.api_core.exceptions.BadRequest: 400 configuration.query.destinationTable cannot be set for scripts</strong></p>
  
  <p>This is the function I use:</p>
  
  <pre><code>def execute_bigquery_sql(query, dataset_id, table_id, use_legacy_sql=True, write_disposition='WRITE_TRUNCATE'):
      client = bigquery.Client()
      job_config = bigquery.QueryJobConfig()
      job_config.use_legacy_sql = use_legacy_sql
  
      print("table_id: {table_id}".format(table_id=table_id))
      print("dataset_id: {dataset_id}".format(dataset_id=dataset_id))
  
      if table_id:
          table_ref = client.dataset(dataset_id).table(table_id)
          print("table_ref: {table_ref}".format(table_ref=table_ref))
          job_config.destination = table_ref
          job_config.write_disposition = write_disposition
          job_config.allow_large_results = True
          job_config.createDisposition = "CREATE_IF_NEEDED"
  
      query_job = client.query(query,job_config=job_config)
      results = query_job.result()  # Waits for job to complete.
  </code></pre>
  
  <p>Does anyone knows what might be happening and a workaround?</p>