Key Error where query jsonb in postgresql with peewee
I have tried with Python 2.7 and Python 3.5.
 Are you absolutely positive that your model class is using `PostgresqlExtDatabase` as it's database class?
 Greate! thanks very much. I have tried several time, and could not find any information with google.
should be:

```
from playhouse.postgres_ext import PostgresqlExtDatabase
dbconnect = PostgresqlExtDatabase(
```

I'm user peewee for PostgreSQL query with Python 3.5 under Debian Jessis. Everythin goes well untill querying Jsonb field.

The script:

```
import peewee
from playhouse.postgres_ext import BinaryJSONField

dbconnect = peewee.PostgresqlDatabase(
    'pycate',
    user='yunsuan',
    password='passhere',
    host='127.0.0.1',
    autocommit=True,
    autorollback=True
)

class BaseModel(peewee.Model):
    class Meta:
        database = dbconnect

class TestTabInfor(BaseModel):
    uid = peewee.CharField(null=False, index=True, unique=True, primary_key=True, max_length=36, help_text='', )
    title = peewee.CharField(null=False, default='')
    infor = BinaryJSONField()
try:
    TestTabInfor.create_table()
except:
    pass

condition = {}
db_data = (TestTabInfor
         .select()
         .where(TestTabInfor.infor.contains(condition)))
print(db_data)
```

It will echo:

`KeyError: 'JB@>'`
