AttributeError: 'NoneType' object has no attribute 'decode' with asyncpg

Describe the bug Application doesn’t start with asyncpg and generate_schemas param.

ERROR:uvicorn.error:Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/starlette/routing.py", line 473, in __call__
    await self.startup()
  File "/usr/local/lib/python3.7/site-packages/starlette/routing.py", line 457, in startup
    await handler()
  File "/usr/local/lib/python3.7/site-packages/tortoise/contrib/starlette/__init__.py", line 80, in init_orm
    await Tortoise.generate_schemas()
  File "/usr/local/lib/python3.7/site-packages/tortoise/__init__.py", line 682, in generate_schemas
    await generate_schema_for_client(connection, safe)
  File "/usr/local/lib/python3.7/site-packages/tortoise/utils.py", line 16, in generate_schema_for_client
    await generator.generate_from_string(schema)
  File "/usr/local/lib/python3.7/site-packages/tortoise/backends/base/schema_generator.py", line 374, in generate_from_string
    await self.client.execute_script(creation_string)
  File "/usr/local/lib/python3.7/site-packages/tortoise/backends/asyncpg/client.py", line 33, in translate_exceptions_
    return await func(self, *args)
  File "/usr/local/lib/python3.7/site-packages/tortoise/backends/asyncpg/client.py", line 173, in execute_script
    await connection.execute(query)
  File "/usr/local/lib/python3.7/site-packages/asyncpg/connection.py", line 272, in execute
    return await self._protocol.query(query, timeout)
  File "asyncpg/protocol/protocol.pyx", line 316, in query
  File "asyncpg/protocol/protocol.pyx", line 807, in asyncpg.protocol.protocol.BaseProtocol._dispatch_result
  File "asyncpg/protocol/protocol.pyx", line 734, in asyncpg.protocol.protocol.BaseProtocol._on_result__simple_query
AttributeError: 'NoneType' object has no attribute 'decode'

[2019-11-29 12:02:31 +0000] [37] [ERROR] Application startup failed. Exiting.
{"loglevel": "info", "workers": 1, "bind": "0.0.0.0:8080", "workers_per_core": 1.0, "host": "0.0.0.0", "port": "8080"}
ERROR:uvicorn.error:Application startup failed. Exiting.
[2019-11-29 12:02:31 +0000] [37] [INFO] Worker exiting (pid: 37)

To Reproduce

DB_MODELS = ["app.models.db.tortoise"]
DB_CONFIG = {
    'connections': {
        'default': {
            'engine': 'tortoise.backends.asyncpg',
            'credentials': {
                'host': 'postgres',
                'port': '5432',
                'user': 'postgres',
                'password': 'postgres',
                'database': 'mydb',
            }
        },
    },
    'apps': {
        'models': {
            'models': DB_MODELS,
            'default_connection': 'default',
        }
    }
}

def init_db(app: FastAPI):
    register_tortoise(
        app, generate_schemas=True, config=DB_CONFIG
    )

NOTE: Folder that should contain the models app.models.db.tortoise is empty (except __init__.py file.)

Expected behavior I think application should start 😄

[grigi]

Please test v0.15.4

It now emits a RuntimeWarning when a module has no models to import, and should not crash like OP, please test 😄

/home/grigi/coding/tortoise/tortoise/contrib/starlette/__init__.py:76: RuntimeWarning: Module "models" has no models
  await Tortoise.init(config=config, config_file=config_file, db_url=db_url, modules=modules)

[prostomarkeloff]

Thanks so much! I have tested it and it works awesome!