SystemStore migration to return plain errors (#14835)

* SystemStore migration to return plain errors

* Fix nilness

* Fix translations

* Fix merge

* Fix layers

* Fix merge errors

* Lint: remove unnecessary use of sprint

* Fix merge errors

* Fix i18n

Co-authored-by: Agniva De Sarker <agnivade@yahoo.co.in>

testlib/store.go

@@ -24,8 +24,8 @@ func (s *TestStore) Close() {
 func GetMockStoreForSetupFunctions() *mocks.Store {
 	mockStore := mocks.Store{}
 	systemStore := mocks.SystemStore{}
-	systemStore.On("GetByName", "AsymmetricSigningKey").Return(nil, model.NewAppError("FakeError", "store.sql_system.get_by_name.app_error", nil, "", http.StatusInternalServerError))
-	systemStore.On("GetByName", "PostActionCookieSecret").Return(nil, model.NewAppError("FakeError", "store.sql_system.get_by_name.app_error", nil, "", http.StatusInternalServerError))
+	systemStore.On("GetByName", "AsymmetricSigningKey").Return(nil, model.NewAppError("FakeError", "app.system.get_by_name.app_error", nil, "", http.StatusInternalServerError))
+	systemStore.On("GetByName", "PostActionCookieSecret").Return(nil, model.NewAppError("FakeError", "app.system.get_by_name.app_error", nil, "", http.StatusInternalServerError))
 	systemStore.On("GetByName", "InstallationDate").Return(&model.System{Name: "InstallationDate", Value: strconv.FormatInt(model.GetMillis(), 10)}, nil)
 	systemStore.On("GetByName", "FirstServerRunTimestamp").Return(&model.System{Name: "FirstServerRunTimestamp", Value: "10"}, nil)
 	systemStore.On("GetByName", "AdvancedPermissionsMigrationComplete").Return(&model.System{Name: "AdvancedPermissionsMigrationComplete", Value: "true"}, nil)