new command «certificate» to install CA certificate for SSL - file needs to be open ...

src/commands.hxx

@@ -1421,7 +1421,8 @@ class Certificate: public Command {
       Logger log(this, script);
       QString filename(script->replacevars(_filename));
       QFile cacertfile(filename);
-      if (!cacertfile.exists()) throw FileNotFound(filename);
+      if (!cacertfile.exists() || !cacertfile.open(QIODevice::ReadOnly))
+        throw FileNotFound(filename);
       QSslCertificate cacert(&cacertfile);
       if (cacert.isNull()) throw NotACertificate(filename);
       QSslSocket::addDefaultCaCertificate(cacert);