Report using /opt/yunohost as install dir as a warning >_>

package_linter.py

@@ -2099,6 +2099,15 @@ def version_format(self):
                 "each time the upstream version changes."
             )
 
+    @test()
+    def custom_install_dir(self):
+        custom_install_dir = self.manifest.get("resources", {}).get("install_dir", {}).get("dir")
+        if not custom_install_dir:
+            return
+
+        if custom_install_dir.startswith("/opt/yunohost"):
+            yield Warning("Installing apps in /opt/yunohost is deprecated ... YunoHost is about standardization, and the standard is to install in /var/www/__APP__ (yes, even if not a webapp, because whatever). Please stick to the default value. the resource system should automatically move the install dir if needed so you don't really need to think about backward compatibility.")
+
     @test()
     def install_args(self):