title: Usage of variable in airflow DAG
body: <p>I set the variable with the "<code>airflow variables</code>" command in <code>cli</code>
  I wants to use this variable in <code>DAG</code>.
  I executed the following command on the terminal
  The error continues occurs.</p>
  
  <pre><code> Broken DAG: [/root/airflow/dags/param_test.py] invalid syntax (param_test.py, line 13) 
  
  airflow variables -s sh_path = "/tmp/echo_test.sh"
  airflow scheduler
  </code></pre>
  
  <p>here the code :</p>
  
  <pre><code>from airflow import DAG
  from airflow.models import Variable
  from airflow.operators.bash_operator import BashOperator
  
  tmpl_search_path = Variable.get ("sh_path")
  
  dag = DAG ('param_test', schedule_interval = '* / 5 * * * *'
             start_date = datetime (2018,9,4), catchup = False)
  
  bash_task = BashOperator (
        task_id = "bash_task"
        bash_command = 'sh '+ {{var.value.tmpl_search_path}},
        dag = dag)
  
  bash_task.set_downstream (python_task)
  
  bash_task1 = BashOperator (
        task_id = 'echo',
        bash_command = 'echo 1',
        dag = dag)
  
  bash_task.set_downstream (bash_task1)
  </code></pre>