there is no cached script available.
<DT><B>Returns:</B><DD>the loaded module script, or null if it can't be found in the
 privileged locations, or <A HREF="../../../../../../org/mozilla/javascript/commonjs/module/provider/ModuleSourceProvider.html#NOT_MODIFIED"><CODE>ModuleSourceProvider.NOT_MODIFIED</CODE></A> if
 the existing cached module script is still valid.
<DT><B>Throws:</B>
<DD><CODE>java.io.IOException</CODE> - if the module script was found, but an I/O exception
 prevented it from being loaded.
