create table ref.foo(id integer identity(1, 1) not null unique);

create table ref.bar(
foo_id integer not null,
foreign key(foo_id) references ref.foo(id))

  File "/home/dario/Projects/l2/Hydra/database/hydra_database/__init__.py", line 81, in cached_metadatas
    redshiftmeta.reflect(only=tablenames, schema=schema)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/sql/schema.py", line 3647, in reflect
    Table(name, self, **reflect_opts)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/sql/schema.py", line 416, in __new__
    metadata._remove_table(name, schema)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 60, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/sql/schema.py", line 411, in __new__
    table._init(name, metadata, *args, **kw)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/sql/schema.py", line 484, in _init
    self._autoload(metadata, autoload_with, include_columns)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/sql/schema.py", line 496, in _autoload
    self, include_columns, exclude_columns
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1477, in run_callable
    return callable_(self, *args, **kwargs)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 364, in reflecttable
    return insp.reflecttable(table, include_columns, exclude_columns)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/engine/reflection.py", line 578, in reflecttable
    exclude_columns, reflection_options)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/engine/reflection.py", line 666, in _reflect_fk
    table_name, schema, **table.dialect_kwargs)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/engine/reflection.py", line 447, in get_foreign_keys
    **kw)
  File "<string>", line 2, in get_foreign_keys
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy/engine/reflection.py", line 54, in cache
    ret = fn(self, con, *args, **kw)
  File "/home/dario/.local/share/virtualenvs/hydra_worker/local/lib/python2.7/site-packages/sqlalchemy_redshift/dialect.py", line 396, in get_foreign_keys
    referred_column = m.group('referred_column')
AttributeError: 'NoneType' object has no attribute 'group'