guide the user in tandem binary installation

src/utils/utils.cpp

@@ -263,7 +263,16 @@ Utils::checkXtandemVersion(const QString &tandem_bin_path)
     {
       // dir.path() returns the unique directory path
       throw pappso::PappsoException(
-        QObject::tr("Please check permissions on !Tandem software found at %1.")
+        QObject::tr("Please check permissions on X!Tandem software found at %1 "
+                    "(file not readable).")
+          .arg(tandem_exe.absoluteFilePath()));
+    }
+  if(!tandem_exe.isExecutable())
+    {
+      // dir.path() returns the unique directory path
+      throw pappso::PappsoException(
+        QObject::tr("Please check permissions on X!Tandem software found at %1 "
+                    "(file not executable).")
           .arg(tandem_exe.absoluteFilePath()));
     }