title: Can't import Airflow plugins
body: <p>Following Airflow tutorial <a href="http://michal.karzynski.pl/blog/2017/03/19/developing-workflows-with-apache-airflow/" rel="noreferrer">here</a>.</p>
  
  <p><strong>Problem</strong>: The webserver returns the following error</p>
  
  <pre><code>Broken DAG: [/usr/local/airflow/dags/test_operator.py] cannot import name 
  MyFirstOperator
  </code></pre>
  
  <p><strong>Notes:</strong>
  The directory structure looks like this:</p>
  
  <pre><code>airflow_home
  ├── airflow.cfg
  ├── airflow.db
  ├── dags
  │   └── test_operators.py  
  ├── plugins
  │   └── my_operators.py   
  └── unittests.cfg
  </code></pre>
  
  <p>I am attempting to import the plugin in 'test_operators.py' like this:</p>
  
  <pre><code>from airflow.operators import MyFirstOperator
  </code></pre>
  
  <p>The code is all the same as what is found in the tutorial.</p>