Fix default raw_template files value in migration

This was causing the following error when trying to do a stack-list:
ERROR: Attribute 'files' does not accept objects of type <type 'unicode'>

Change-Id: Ideee81e44e85fcd8d8f3c9c196702a6c78e5adfd
Closes-Bug: #1277278
# vim: tabstop=4 shiftwidth=4 softtabstop=4

#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import sqlalchemy
from heat.db.sqlalchemy.types import Json


def upgrade(migrate_engine):
    meta = sqlalchemy.MetaData()
    meta.bind = migrate_engine

    raw_template = sqlalchemy.Table('raw_template', meta, autoload=True)
    files = sqlalchemy.Column('files', Json, default={})
    files.create(raw_template)


def downgrade(migrate_engine):
    meta = sqlalchemy.MetaData()
    meta.bind = migrate_engine

    raw_template = sqlalchemy.Table('raw_template', meta, autoload=True)
    raw_template.c.files.drop()

# vim: tabstop=4 shiftwidth=4 softtabstop=4

#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import sqlalchemy
from heat.db.sqlalchemy.types import Json


def upgrade(migrate_engine):
    meta = sqlalchemy.MetaData()
    meta.bind = migrate_engine

    raw_template = sqlalchemy.Table('raw_template', meta, autoload=True)
    files = sqlalchemy.Column('files', Json, default='{}')
    files.create(raw_template)


def downgrade(migrate_engine):
    meta = sqlalchemy.MetaData()
    meta.bind = migrate_engine

    raw_template = sqlalchemy.Table('raw_template', meta, autoload=True)
    raw_template.c.files.drop()
