Report installing custom python versions as a warning...

package_linter.py

@@ -745,6 +745,16 @@ def disclaimer_wording_or_placeholder(app):
                     "The doc/ folder seems to still contain some dummy, placeholder messages in the .md markdown files. If those files are not useful in the context of your app, simply remove them."
                 )
 
+    @test()
+    def custom_python_version(app):
+
+        cmd = f"grep -q -IhEr '^[^#]*install_python' '{app.path}/scripts/'"
+        if os.system(cmd) == 0:
+            yield Warning(
+                "It looks like this app installs a custom version of Python which is heavily discouraged, both because it takes a shitload amount of time to compile Python locally, and because it is likely to create complication later once the system gets upgraded to newer Debian versions..."
+            )
+
+
     @test()
     def change_url_script(app):