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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def page_not_found(request, template_name='404.html'):
 """ Default 404 handler. Templates: :template:`404.html` Context: request_path The path of the requested URL (e.g., '/app/pages/bad_page/') """

    response = render_in_page(request, template_name)

    if response:
        return response

    template = Template(
        '<h1>Not Found</h1>'
        '<p>The requested URL {{ request_path }} was not found on this server.</p>')
    body = template.render(RequestContext(
        request, {'request_path': request.path}))
    return http.HttpResponseNotFound(body, content_type=CONTENT_TYPE)