While working with hibernate you will sometimes have an error message like the following:
javax.persistence.PersistenceException: No Persistence provider for EntityManager named <YOUR PERSISTENT UNIT NAME>
One of the possible causes for this is that the provider for hibernate in your persistence.xml is wrong. In various places on the web it is suggested that it should be: org.hibernate.ejb.HibernatePersistence
Putting the one above results in the obscure exception above.
To fix this enter the correct provider for hibernate: org.hibernate.jpa.HibernatePersistenceProvider