Primer update config - enable pytest (#1626)

Reformatted projects I have acceess to:
- aioexabgp
- bandersnatch
- flake8-bugbear

```
-- primer results 📊 --

13 / 16 succeeded (81.25%) ✅
0 / 16 FAILED (0.0%) 💩
 - 3 projects disabled by config
 - 0 projects skipped due to Python version
 - 0 skipped due to long checkout
```

* Also re-enable pytest

```
-- primer results 📊 --

14 / 16 succeeded (87.5%) ✅
0 / 16 FAILED (0.0%) 💩
 - 2 projects disabled by config
 - 0 projects skipped due to Python version
 - 0 skipped due to long checkout

real	2m26.207s
user	17m55.404s
sys	0m43.061s
```