PythonObjectSerializer raise 'utf-8' codec can't decode byte

Good time of the day team

When I tried to cache API responses, it failed as sometimes I have UnicodeDecodeError.

Looking deeper, I found that this is happening because of this code `out.write_string(cPickle.dumps(obj, 0).decode("utf-8"))` in `PythonObjectSerializer`
Full Code:
```python
class PythonObjectSerializer(BaseSerializer):
def read(self, inp):
str = inp.read_string().encode()
return cPickle.loads(str)

def write(self, out, obj):
out.write_string(cPickle.dumps(obj, 0).decode("utf-8"))

def get_type_id(self):
return PYTHON_TYPE_PICKLE
```

Issue example:
```console
>>> import pickle

>>> pickle.dumps("\u00e4").decode("utf-8")

Traceback (most recent call last):

File "", line 1, in

UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 0: invalid start byte
````

As a workaround, I created such a custom serializer:
```
class HazelcastJsonSerializer(StreamSerializer):

def read(self, inp):
return json.loads(inp.read_string())

def write(self, out, obj):
out.write_string(json.dumps(obj))

def get_type_id(self):
…
```

Is there any better solution?

python version: 3.6