TypeError: an integer is required (got type bytes)

Since upgrading to python 3.8 I can't access pickle files created with python 3.7.
This originated from [this issue](https://github.com/facebookincubator/submitit/issues/39) and might be related to [this one](https://github.com/cloudpipe/cloudpickle/issues/266).

## Repro
In python 3.7 (cloudpickle==1.6.0):
```
import cloudpickle

def foo():
pass

with open("foo.pkl", "wb") as ofile:
cloudpickle.dump(foo, ofile)
```

In python 3.8 (cloudpickle==1.6.0):
```
import cloudpickle

with open("foo.pkl", "rb") as ifile:
print(cloudpickle.load(ifile))
```
Throws
```
Traceback (most recent call last):
File "", line 2, in
TypeError: an integer is required (got type bytes)
```
---
Is there any way to migrate those pickle files to use them with python 3.8?