title: BigQuery Operator in Airflow not reading sql as raw file
body: <p>my aim here is to store sql code in GCS and pass into the 'sql' parameter using the  Bigquery Operator for my daily ETL processes.</p>
  <p>My error is</p>
  <pre><code>Exception: BigQuery job failed. Final error was: {'reason': 'invalidQuery', 'location': 'query', 'message': 'Syntax error: Expected end of input but got &quot;/&quot; at [1:1]'}
  </code></pre>
  <p>The issue I currently have is that the sql code, which is a simple</p>
  <pre><code>Select * 
  FROM 
  table
  </code></pre>
  <p>is having the newline <code>/n</code> being read as part of the sql file, so it's failing as an invalid query. When I read the sql file in python, it's being read as follows</p>
  <pre><code>'SELECT * \nFROM \n    `table` as test\n'
  </code></pre>
  <p>My task is as follows</p>
  <pre><code>t1 = BigQueryOperator(
    task_id='bigquery_test',
    sql= '/home/airflow/.../filename.sql ',
    destination_dataset_table = destination_table,
    write_disposition='WRITE_TRUNCATE',
    use_legacy_sql=False,
    dag=dag,
  )
  </code></pre>
  <p>I'm assuming this is something to do with how the sql param is set up in airflow but I cannot wrap my head around what I need to do to get around this issue.</p>
  <p>any help greatly appreciated.</p>