title: Eclipse - How to fix error "No persistence.xml file found in project" JPA issue
body: <p>Error "No persistence.xml file found in project" in Eclipse.</p>
  
  <p>Aim: Create a new project GWT+App engine+Maven </p>
  
  <p>Steps to create this:</p>
  
  <ol>
  <li>Google eclipse plugin: select "New Web Application Project". </li>
  <li>set the name etc.  </li>
  <li>right-click on the project > Configure >
  Convert to Maven... </li>
  <li>Fix jdoconfig.xml file: xsi has the wrong
  value. see
  <a href="https://stackoverflow.com/questions/6042475/validating-jdoconfig-with-incorrect-url">Validating jdoconfig with incorrect url</a></li>
  </ol>
  
  <p>Then I get the above error.</p>
  
  <p>The file exists at scr/META-INF/persistence.xml
  and also war/WEB-INF/classes/META-INF/persistence.xml
  But is not being found.</p>
  
  <p>Notes: I installed plugins m2e, m2e-wtp and google eclipse plugin </p>