[pypy-issue] Issue #3052: json skipkeys=True results in invalid json with a trailing comma on pypy3 (pypy/pypy)

[Glyph]

New issue 3052: json skipkeys=True results in invalid json with a trailing comma on pypy3
https://bitbucket.org/pypy/pypy/issues/3052/json-skipkeys-true-results-in-invalid-json

Glyph:

‌

```python
import json
print(json.dumps({
    "hello": "what",
    b"world": "what",
}, skipkeys=True))
```

‌

```
$ python3 j3.py
{"hello": "what"}
$ pypy3 j3.py
{"hello": "what", }
```