Custom generator with a custom Config cannot be generated

[RobertCraigie]

Bug description

$ prisma generate

✔ Generated Prisma Client Python (v0.6.4) to ./.nox/pytest/lib/python3.10/site-packages/prisma in 223ms

    config = get_config()
  File ".nox/pytest/lib/python3.10/site-packages/prisma/generator/models.py", line 109, in get_config
    return config_ctx.get()
LookupError: <ContextVar name='config_ctx' at 0x10292e8e0>

How to reproduce

datasource db {
  provider = "sqlite"
  url      = "file:database.db"
}

generator py {
  provider             = "prisma-client-py"
  interface            = "asyncio"
  recursive_type_depth = -1
}

generator custom {
  provider = "python generator.py"
}

model User {
  id    String  @id @default(cuid())
  name  String
}

# generator.py
from jinja2 import Environment, FileSystemLoader
from prisma.generator import (
    GenericGenerator,
    GenericData,
    Manifest,
)
from prisma.generator.models import BaseModel

class Config(BaseModel):
    ...

class Data(GenericData[Config]):
    ...

class Generator(GenericGenerator[Data]):
    def get_manifest(self) -> Manifest:
        return Manifest(
            name='Custom',
            default_output=PKG_DIR,
            requires_generators=['prisma-client-py'],
        )

    def generate(self, data: Data) -> None:
        ...

Generator.invoke()

Expected behavior

Custom generator can be generated.

[RobertCraigie]

This may actually be fixed - needs investigation.