How to use the xandikos.store.InvalidFileContents function in xandikos

for (name, mode, sha) in self._iterblobs():
            etag = sha.decode('ascii')
            if name in removed:
                removed.remove(name)
            if (name in self._fname_to_uid and
                    self._fname_to_uid[name][0] == etag):
                continue
            blob = self.repo.object_store[sha]
            fi = open_by_extension(blob.chunked, name,
                                   self.extra_file_handlers)
            try:
                uid = fi.get_uid()
            except KeyError:
                logger.warning('No UID found in file %s', name)
                uid = None
            except InvalidFileContents:
                logging.warning('Unable to parse file %s', name)
                uid = None
            except NotImplementedError:
                # This file type doesn't support UIDs
                uid = None
            self._fname_to_uid[name] = (etag, uid)
            if uid is not None:
                self._uid_to_fname[uid] = (name, etag)
        for name in removed:
            (unused_etag, uid) = self._fname_to_uid[name]
            if uid is not None:
                del self._uid_to_fname[uid]
            del self._fname_to_uid[name]

def calendar(self):
        if self._calendar is None:
            try:
                self._calendar = Calendar.from_ical(b''.join(self.content))
            except ValueError as e:
                raise InvalidFileContents(
                    self.content_type, self.content, str(e))
        return self._calendar

def validate(self):
        c = b''.join(self.content).strip()
        # TODO(jelmer): Do more extensive checking of VCards
        if not c.startswith((b'BEGIN:VCARD\r\n', b'BEGIN:VCARD\n')) or \
           not c.endswith(b'\nEND:VCARD'):
            raise InvalidFileContents(
                self.content_type, self.content,
                "Missing header and trailer lines")

def validate(self):
        """Verify that file contents are valid."""
        cal = self.calendar
        # TODO(jelmer): return the list of errors to the caller
        if cal.is_broken:
            raise InvalidFileContents(
                self.content_type, self.content,
                "Broken calendar file")
        errors = list(validate_calendar(cal, strict=False))
        if errors:
            raise InvalidFileContents(
                self.content_type, self.content,
                ", ".join(errors))

def validate(self):
        """Verify that file contents are valid."""
        cal = self.calendar
        # TODO(jelmer): return the list of errors to the caller
        if cal.is_broken:
            raise InvalidFileContents(
                self.content_type, self.content,
                "Broken calendar file")
        errors = list(validate_calendar(cal, strict=False))
        if errors:
            raise InvalidFileContents(
                self.content_type, self.content,
                ", ".join(errors))

def _scan_uids(self):
        removed = set(self._fname_to_uid.keys())
        for (name, content_type, etag) in self.iter_with_etag():
            if name in removed:
                removed.remove(name)
            if (name in self._fname_to_uid and
                    self._fname_to_uid[name][0] == etag):
                continue
            fi = open_by_extension(self._get_raw(name, etag), name,
                                   self.extra_file_handlers)
            try:
                uid = fi.get_uid()
            except KeyError:
                logger.warning('No UID found in file %s', name)
                uid = None
            except InvalidFileContents:
                logging.warning('Unable to parse file %s', name)
                uid = None
            except NotImplementedError:
                # This file type doesn't support UIDs
                uid = None
            self._fname_to_uid[name] = (etag, uid)
            if uid is not None:
                self._uid_to_fname[uid] = (name, etag)
        for name in removed:
            (unused_etag, uid) = self._fname_to_uid[name]
            if uid is not None:
                del self._uid_to_fname[uid]
            del self._fname_to_uid[name]