title: setup pythonpath before starting test suite
body: <p>Currently I am setting pythonpath as <code>pybot --pythonpath ~/Test_suite  main.robot</code> while running the tests. </p>
  
  <p>I also see there is option     <code>Set Environment Variable    PYTHONPATH    ${CURDIR}</code> to set through robot framework. But it doesn't run before main settings</p>
  
  <pre><code>*** Settings ***
  Documentation    Suite description
  Resource         settings.robot
  </code></pre>
  
  <p>And below is settings.robot file</p>
  
  <pre><code>*** Settings ***
  Resource         keywords/keywords_test.robot
  Library          tests.test_1.TestClass
  </code></pre>
  
  <p>How to setup the pythonpath before running the suite?</p>