Process the uploaded file.

def process_upload(self, set_content_type=True):
        """Process the uploaded file."""
        metadata = self.get_upload_key_metadata()

        if set_content_type:
            content_type = self.get_upload_content_type()
            metadata.update({b'Content-Type': b'{0}'.format(content_type)})

        upload_key = self.get_upload_key()
        processed_key_name = self.get_processed_key_name()
        processed_key = upload_key.copy(upload_key.bucket.name,
                                        processed_key_name, metadata)
        processed_key.set_acl(self.get_processed_acl())
        upload_key.delete()
        return processed_key