Find errors correctly when deleting an environment

The error message was not fetched appropriately when trying to see if
there were any errors upon deleting an environment.

This corrects that, as apollo shoves the errors into the following
shape:

{
  data: {
    deleteEnvironment: {
      errors: [messages]
    }
  }
}

This is now also tested for.

app/assets/javascripts/environments/components/delete_environment_modal.vue

@@ -62,7 +62,8 @@ export default {
             mutation: deleteEnvironmentMutation,
             variables: { environment: this.environment },
           })
-          .then(([message]) => {
+          .then(({ data }) => {
+            const [message] = data?.deleteEvironment?.errors ?? [];
             if (message) {
               createFlash({ message });
             }

spec/frontend/environments/delete_environment_modal_spec.js

@@ -5,8 +5,11 @@ import VueApollo from 'vue-apollo';
 import { s__, sprintf } from '~/locale';
 import DeleteEnvironmentModal from '~/environments/components/delete_environment_modal.vue';
 import createMockApollo from 'helpers/mock_apollo_helper';
+import waitForPromises from 'helpers/wait_for_promises';
+import createFlash from '~/flash';
 import { resolvedEnvironment } from './graphql/mock_data';
 
+jest.mock('~/flash');
 Vue.use(VueApollo);
 
 describe('~/environments/components/delete_environment_modal.vue', () => {
@@ -54,6 +57,34 @@ describe('~/environments/components/delete_environment_modal.vue', () => {
 
     await nextTick();
 
+    expect(createFlash).not.toHaveBeenCalled();
+
+    expect(deleteResolver).toHaveBeenCalledWith(
+      expect.anything(),
+      { environment: resolvedEnvironment },
+      expect.anything(),
+      expect.anything(),
+    );
+  });
+
+  it('should flash a message on error', async () => {
+    createComponent({ apolloProvider: mockApollo });
+
+    deleteResolver.mockRejectedValue();
+
+    wrapper.findComponent(GlModal).vm.$emit('primary');
+
+    await waitForPromises();
+
+    expect(createFlash).toHaveBeenCalledWith(
+      expect.objectContaining({
+        message: s__(
+          'Environments|An error occurred while deleting the environment. Check if the environment stopped; if not, stop it and try again.',
+        ),
+        captureError: true,
+      }),
+    );
+
     expect(deleteResolver).toHaveBeenCalledWith(
       expect.anything(),
       { environment: resolvedEnvironment },