问为什么应用程序引擎部署时出现Persistence.createEntityManagerFactory("transactions-optional")错误？

EN

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
        http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" version="2.0">

    <persistence-unit name="transactions-optional" transaction-type="RESOURCE_LOCAL">
        <provider></provider>
        <class>com.example.myapp.Class1</class>
        <class>com.example.myapp.Class2</class>
        <properties>
            <property name="datanucleus.NontransactionalRead" value="true"/>
            <property name="datanucleus.NontransactionalWrite" value="true"/>
            <property name="javax.persistence.jdbc.driver" value="com.google.appengine.api.rdbms.AppEngineDriver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:google:rdbms://something.com:someproj:someapp/somedb"/>
            <property name="javax.persistence.jdbc.user" value=""/>
            <property name="javax.persistence.jdbc.password" value=""/>
        </properties>
    </persistence-unit>
</persistence>