keystone安装错误

通过源码安装keystone
执行keystone-manage db_sync时报错
Traceback (most recent call last):
  File "/usr/local/bin/keystone-manage", line 5, in <module>
    pkg_resources.run_script('keystone==2012.2', 'keystone-manage')
  File "/usr/local/lib/python2.7/site-packages/setuptools-0.6c11-py2.7.egg/pkg_resources.py", line 489, in run_script
  File "/usr/local/lib/python2.7/site-packages/setuptools-0.6c11-py2.7.egg/pkg_resources.py", line 1207, in run_script
  File "/usr/local/lib/python2.7/site-packages/keystone-2012.2-py2.7.egg/EGG-INFO/scripts/keystone-manage", line 28, in <module>
    cli.main(argv=sys.argv, config_files=config_files)
  File "/usr/local/lib/python2.7/site-packages/keystone-2012.2-py2.7.egg/keystone/cli.py", line 164, in main
    return run(cmd, (args[:1] + args[2:]))
  File "/usr/local/lib/python2.7/site-packages/keystone-2012.2-py2.7.egg/keystone/cli.py", line 147, in run
    return CMDS[cmd](argv=args).run()
  File "/usr/local/lib/python2.7/site-packages/keystone-2012.2-py2.7.egg/keystone/cli.py", line 35, in run
    return self.main()
  File "/usr/local/lib/python2.7/site-packages/keystone-2012.2-py2.7.egg/keystone/cli.py", line 54, in main
    driver = importutils.import_object(getattr(CONF, k).driver)
  File "/usr/local/lib/python2.7/site-packages/keystone-2012.2-py2.7.egg/keystone/openstack/common/importutils.py", line 40, in import_object
    return import_class(import_str)(*args, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/keystone-2012.2-py2.7.egg/keystone/openstack/common/importutils.py", line 30, in import_class
    __import__(mod_str)
  File "/usr/local/lib/python2.7/site-packages/keystone-2012.2-py2.7.egg/keystone/identity/backends/sql.py", line 22, in <module>
    from keystone.common.sql import migration
  File "/usr/local/lib/python2.7/site-packages/keystone-2012.2-py2.7.egg/keystone/common/sql/migration.py", line 23, in <module>
    from migrate.versioning import api as versioning_api
  File "/usr/local/lib/python2.7/site-packages/migrate/versioning/api.py", line 33, in <module>
    from migrate.versioning import (repository, schema, version,
  File "/usr/local/lib/python2.7/site-packages/migrate/versioning/schema.py", line 10, in <module>
    from sqlalchemy import exceptions as sa_exceptions
ImportError: cannot import name exceptions该怎么解决openstack    keystonopenstackkeystone