neutron.db.migration.migrate_to_ml2 foreign key error

[root@gpu2 neutron]# python -m neutron.db.migration.migrate_to_ml2 openvswitch   mysql://quantum:mquserpassword@gpu4/ovs_quantum
Traceback (most recent call last):
  File "/usr/lib64/python2.6/runpy.py", line 122, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib64/python2.6/runpy.py", line 34, in _run_code
    exec code in run_globals
  File "/usr/lib/python2.6/site-packages/neutron/db/migration/migrate_to_ml2.py", line 462, in <module>
    main()
  File "/usr/lib/python2.6/site-packages/neutron/db/migration/migrate_to_ml2.py", line 458, in main
    args.vxlan_udp_port)
  File "/usr/lib/python2.6/site-packages/neutron/db/migration/migrate_to_ml2.py", line 138, in __call__
    metadata.create_all(engine)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/schema.py", line 2848, in create_all
    tables=tables)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/base.py", line 1479, in _run_visitor
    conn._run_visitor(visitorcallable, element, **kwargs)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/base.py", line 1122, in _run_visitor
    **kwargs).traverse_single(element)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/sql/visitors.py", line 122, in traverse_single
    return meth(obj, **kw)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/ddl.py", line 70, in visit_metadata
    self.traverse_single(table, create_ok=True)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/sql/visitors.py", line 122, in traverse_single
    return meth(obj, **kw)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/ddl.py", line 89, in visit_table
    self.connection.execute(schema.CreateTable(table))
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/base.py", line 662, in execute
    params)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/base.py", line 720, in _execute_ddl
    compiled
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/base.py", line 874, in _execute_context
    context)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/base.py", line 1024, in _handle_dbapi_exception
    exc_info
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/util/compat.py", line 196, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/base.py", line 867, in _execute_context
    context)
  File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/default.py", line 324, in do_execute
    cursor.execute(statement, parameters)
  File "/usr/lib64/python2.6/site-packages/MySQLdb/cursors.py", line 173, in execute
    self.errorhandler(self, exc, value)
  File "/usr/lib64/python2.6/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue
sqlalchemy.exc.OperationalError: (OperationalError) (1005, "Can't create table 'ovs_quantum.ml2_network_segments' (errno: 150)") '\nCREATE TABLE ml2_network_segments (\n\tid VARCHAR(36) NOT NULL, \n\tnetwork_id VARCHAR(36) NOT NULL, \n\tnetwork_type VARCHAR(32) NOT NULL, \n\tphysical_network VARCHAR(64), \n\tsegmentation_id INTEGER, \n\tPRIMARY KEY (id), \n\tFOREIGN KEY(network_id) REFERENCES networks (id) ON DELETE CASCADE\n)\n\n' ()
[root@gpu2 neutron]# python -m neutron.db.migration.migrate_to_ml2 openvswitch   mysql://quantum:mquserpassword@gpu4/ovs_quantum