ZCML File
session.zcml

<configure
    xmlns="http://namespaces.zope.org/zope"
    i18n_domain="zope"
    >
<utility
    factory=".session.SessionCredentialsPlugin"
    provides=".interfaces.ICredentialsPlugin"
    name="Session Credentials"
    />
<class
    class=".session.SessionCredentialsPlugin"
    >
<require
    permission="zope.ManageServices"
    interface=".session.IBrowserFormChallenger"
    set_schema=".session.IBrowserFormChallenger"
    />
</class>
<include
    file="session.zcml"
    package=".browser"
    />
</configure>