zoph: Don't fail at showing app view during uninstall

During uninstall step, zoph command may not be available and is_configured() may
error out. In such cases, let the base class AppView show the operations view.

Tests:

- Introduce a sleep in overridden uninstall() method for zoph. Notice that there
is an error showing the view during uninstall. Apply patch and the error is no
longer shown.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/modules/zoph/privileged.py

@@ -90,11 +90,15 @@ def set_configuration(enable_osm: Optional[bool] = None,
 
 
 @privileged
-def is_configured() -> bool:
+def is_configured() -> Optional[bool]:
     """Return whether zoph app is configured."""
-    process = subprocess.run(['zoph', '--get-config', 'interface.user.remote'],
-                             stdout=subprocess.PIPE, check=True)
-    return process.stdout.decode().strip() == 'true'
+    try:
+        process = subprocess.run(
+            ['zoph', '--get-config', 'interface.user.remote'],
+            stdout=subprocess.PIPE, check=True)
+        return process.stdout.decode().strip() == 'true'
+    except FileNotFoundError:
+        return None
 
 
 @privileged

plinth/modules/zoph/views.py

@@ -48,9 +48,12 @@ class ZophAppView(views.AppView):
 
     def dispatch(self, request, *args, **kwargs):
         """Redirect to setup page if setup is not done yet."""
-        if not privileged.is_configured():
+        is_configured = privileged.is_configured()
+        if is_configured is False:
             return redirect('zoph:setup')
 
+        # During operations such as uninstall, zoph command may not be
+        # available, let the base class show operations view instead.
         return super().dispatch(request, *args, **kwargs)
 
     def get_initial(self):