in src/main/java/org/apache/sling/jcr/webdav/impl/servlets/SlingWebDavServlet.java [296:304]
protected void sendUnauthorized(WebdavRequest request, WebdavResponse response, DavException error) throws IOException {
response.setHeader("WWW-Authenticate", getAuthenticateHeaderValue());
response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
if (error != null) {
response.getWriter().write(error.getStatusPhrase());
response.getWriter().write("\n");
}
response.getWriter().flush();
}