SQLAlchemy deals with Enums oddly

sqlalchemy_enum_test.py

import subprocess

from sqlalchemy import create_engine
from sqlalchemy import Column
from sqlalchemy import Enum
from sqlalchemy import types
from sqlalchemy.exc import DataError
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

DATABASE_NAME = 'sqlalchemy_enum_test'
ENUM_VALUES = ('a', 'b', 'c')
ENUM_NAME = 'me_thing_enum'

engine = create_engine('postgresql://localhost:5432/{}'.format(DATABASE_NAME))

Session = sessionmaker(engine)

Base = declarative_base(engine)

class Me(Base):
    __tablename__ = 'me'
    id = Column(types.Integer, primary_key=True)
    thing = Column(Enum(*ENUM_VALUES, name=ENUM_NAME))

def create_tables():
    Base.metadata.create_all(engine)

def recreate_database():
    subprocess.call(['psql', '-c', 'DROP DATABASE {}'.format(DATABASE_NAME)])
    subprocess.call(['psql', '-c', 'CREATE DATABASE {}'.format(DATABASE_NAME)])
    create_tables()

def add_enum_value(value='d'):
    subprocess.call([
        'psql',
        '-d',
        DATABASE_NAME,
        '-c',
        "ALTER TYPE {} ADD VALUE IF NOT EXISTS '{}';".format(ENUM_NAME, value)
    ])

def insert(*things):
    session = Session()
    for thing in things:
        session.add(Me(thing=thing))
    session.commit()

def get_all():
    session = Session()
    return session.query(Me).all()

def test():
    recreate_database()
    assert len(get_all()) == 0
    insert('a', 'b')
    assert len(get_all()) == 2
    try:
        insert('d')
    except DataError:
        pass
    add_enum_value('d')
    insert('d')
    try:
        get_all()
    except:
        print('WTF SQLAlchemy?')


if __name__ == '__main__':
    test()