Errors executing make test

When executing **make test** I suspect related to the PyJWT version. 

I've similar issues in assembler and auth services. 

```
>       token = jwt.encode(ret, private_key, algorithm='RS256').decode('ascii')
E       AttributeError: 'str' object has no attribute 'decode'
```

I'm using PyJWT 2.0.1. I probably should downgrade to another version. 

João
