ZCML File
httpplugins.zcml

<configure
    xmlns="http://namespaces.zope.org/zope"
    i18n_domain="zope"
    >
<utility
    factory=".httpplugins.HTTPBasicAuthCredentialsPlugin"
    provides=".interfaces.ICredentialsPlugin"
    name="Zope Realm Basic-Auth"
    />
<class
    class=".httpplugins.HTTPBasicAuthCredentialsPlugin"
    >
<require
    permission="zope.ManageServices"
    interface=".httpplugins.IHTTPBasicAuthRealm"
    set_schema=".httpplugins.IHTTPBasicAuthRealm"
    />
</class>
<include
    file="httpplugins.zcml"
    package=".browser"
    />
</configure>