Fix errors setting Google Drive permissions not being reported

If an error occurred when attemping to change file permissions after selecting a
file from Google Drive, the LMS frontend incorrectly assumed the attempt had
succeeded. This is because the `request.execute` API doesn't work as the code
expected. It always invokes its first argument with the response. The
`request.then` API is the correct Promise-like API. The argument passed to the
rejection handler then needs to be processed to turn the result into an `Error`
as expected by the calling code.

lms/static/scripts/frontend_apps/utils/google-picker-client.ts

@@ -247,9 +247,21 @@ export class GooglePickerClient {
       fileId: docId,
       resource: body,
     });
-    return new Promise((resolve, reject) => {
-      // @ts-expect-error - We're missing types for this.
-      request.execute(resolve, reject);
+    const result = new Promise((resolve, reject) => {
+      // @ts-expect-error - We're missing types for this, but see
+      // https://github.com/google/google-api-javascript-client/blob/96cf6057f03c5e56179e83869828a06c47ce571b/docs/reference.md.
+      //
+      // For the types of arguments passed to resolve/reject, see
+      // https://github.com/google/google-api-javascript-client/blob/96cf6057f03c5e56179e83869828a06c47ce571b/docs/promises.md#using-promises-1.
+      request.then(resolve, reject);
     });
+
+    try {
+      await result;
+    } catch (response) {
+      throw new Error(
+        response.result?.error?.message ?? 'Unable to make file public',
+      );
+    }
   }
 }

lms/static/scripts/frontend_apps/utils/test/google-picker-client-test.js

@@ -342,7 +342,7 @@ describe('GooglePickerClient', () => {
 
     beforeEach(() => {
       createPermission = fakeGoogleLibs.client.drive.permissions.create;
-      const apiRequest = { execute: resolve => resolve() };
+      const apiRequest = { then: resolve => resolve() };
       createPermission.returns(apiRequest);
     });
 
@@ -394,8 +394,14 @@ describe('GooglePickerClient', () => {
       const client = createClient();
       await client.requestAuthorization();
       createPermission.returns({
-        execute: (_, reject) =>
-          reject(new Error('Changing permissions failed')),
+        then: (_, reject) =>
+          reject({
+            result: {
+              error: {
+                message: 'Changing permissions failed',
+              },
+            },
+          }),
       });
       let err;
       try {