title: Airflow Broken DAG: no module named somepackage
body: <p>I have added my own package to /usr/local/lib/python3.7/site-packages (which is in sys.path):</p>
  
  <p>somepackage
    <strong>init</strong>.py
    helper.py</p>
  
  <p>The following DAG is located in /usr/local/airflow/dags/dev</p>
  
  <pre><code>import sys
  print(sys.path)
  import somepackage.helper as nf
  print(nf.__file__)
  import numpy as np
  print(np.sqrt(2))
  import datetime as dt
  from airflow import DAG
  from airflow.operators.bash_operator import BashOperator
  from airflow.operators.python_operator import PythonOperator
  
  stage = 'dev'
  
  # An usual python method which can be executed:
  def print_world():
      print('world')
  
  
  # Meta informations for airflow:
  default_args = {
      'owner': f'{stage}',
      'start_date': dt.datetime(2020,2,13),
      'retries': 1,
      'retry_delay': dt.timedelta(minutes=5),
      'queue': stage
  }
  
  # The definition and 'script' of the DAG:
  with DAG(f'test_{stage}',
           default_args=default_args,
           schedule_interval=None) as dag:
  
      # Define the steps in the pipeline, see airflow docs for more operators:
      print_hello = BashOperator(task_id='print_hello', bash_command='echo "hello"')
      print_world = PythonOperator(task_id='print_world', python_callable=print_world)
      makefile = BashOperator(task_id='makefile', bash_command='touch /usr/local/airflow/dags/justToTest.txt')
  
  # Pipeline: first do x then do y then do z ....
  print_hello &gt;&gt; print_world &gt;&gt; makefile
  </code></pre>
  
  <p>I can see the file in the Web UI and all print statements in the log. However Airflow keeps saying in the Web UI that the module is not found in the read header.</p>