plinth: Fix translating app operations

Fixes #2420.

Tests performed using Debian stable:
- Set user language to espanol. Install, repair and remove gitweb app.
  Check that all app operation messages are in spanish.
- All unit tests pass.

Signed-off-by: Veiko Aasa <veiko17@disroot.org>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/operation.py

@@ -137,7 +137,7 @@ class Operation:
         """
         from django.utils.translation import gettext
         message = gettext(self.message)
-        message = message.format(name=self.name,
+        message = message.format(name=gettext(self.name),
                                  exception_message=str(self.exception))
         if self.app_id:
             message = message.format(