message: warn on logout too
diff: @@ -22,6 +22,7 @@ import Notifier from './Notifier';
  import UserActivity from './UserActivity';
  import Presence from './Presence';
  import dis from './dispatcher';
  +import Modal from './Modal';
  import DMRoomMap from './utils/DMRoomMap';
  /**
  @@ -289,7 +290,20 @@ export function logout() {
  return;
  }
  - return MatrixClientPeg.get().logout().then(onLoggedOut,
  + var QuestionDialog = sdk.getComponent("dialogs.QuestionDialog");
  + Modal.createDialog(QuestionDialog, {
  + title: "Warning",
  + description:
  + <div>
  + For security, logging out will delete any end-to-end encryption keys from this browser,
  + making previous encrypted chat history unreadable if you log back in.
  + In future this <a href="https://github.com/vector-im/riot-web/issues/2108">will be improved</a>,
  + but for now be warned.
  + </div>,
  + button: "Continue",
  + onFinished: (confirmed) => {
  + if (confirmed) {
  + MatrixClientPeg.get().logout().then(onLoggedOut,
  (err) => {
  // Just throwing an error here is going to be very unhelpful
  // if you're trying to log out because your server's down and
  @@ -303,6 +317,9 @@ export function logout() {
  }
  );
  }
  + },
  + });
  +}
  /**
  * Starts the matrix client and all other react-sdk services that
  