Fix calendar app

This is a regression from commit e09172646b78a42d9eea6d5b1a10cddf21890b07.

Although the stoq process doesn't need to import Branch, because for sure it's
already loaded, the calendar runs on another process that doesn't know about it

Change-Id: I11bafcdde3c07e43870e6c024b8ceb06ad2c5e8a