I have some bug with pony ORM, I'll file a new issue I think

pony_orm_bug.py

# I have a problem with this code with Python 3.6.5, pony 0.7.6
# An exception is thrown:
# "pony.orm.core.TransactionError: db_session is required when working with the database"
# in the "I shall feed thee!" line.
# also see https://github.com/ponyorm/pony/issues/126

import asyncio
from pony.orm import commit, db_session, select, Database, Required

db = Database()
db.bind(provider='sqlite', filename=':memory:', create_db=True)


class Cat(db.Entity):
    name = Required(str)
    age = Required(int)


db.generate_mapping(create_tables=True)


with db_session: # this is good
    meow = Cat(name="meow", age=31)
    purr = Cat(name="purr", age=14)
    commit()
    print("hoho here they are!", list(select(cat.name for cat in Cat)))


@db_session
async def feed_cats(): # this is bad
    print("I shall feed thee!", list(select(cat.name for cat in Cat)))
    await asyncio.sleep(2)

loop = asyncio.get_event_loop()
loop.run_until_complete(feed_cats())
loop.close()