javax.persistence.PersistenceException in google app engine connected android project -

i created google app engine connected android project. when run code got exception. 1 tell how can come through problem. alot

com.google.api.client.googleapis.json.googlejsonresponseexception: 503 service unavailable { "code" : 503, "errors" : [ { "domain" : "global", "message" : "javax.persistence.persistenceexception: no persistence providers available \"jpatest\" after trying following discovered implementations: org.datanucleus.api.jpa.persistenceproviderimpl", "reason" : "backenderror" } ], "message" : "javax.persistence.persistenceexception: no persistence providers available \"jpatest\" after trying following discovered implementations: org.datanucleus.api.jpa.persistenceproviderimpl"