Preventing installing v2.0.0 of PyJWT
Preventing installing v2.0.0 of PyJWT

PyJWT 2.0.0 has a breaking change for the current release, pin to a version less than 2.0

```
File "/usr/local/lib/python3.6/site-packages/social_core/backends/azuread_tenant.py", line 6, in <module>
    from jwt import DecodeError, ExpiredSignature, decode as jwt_decode
ImportError: cannot import name 'ExpiredSignature'
```
python-social-auth/social-core,python-social-auth/social-core