formatOnType strips spaces around `=` when used in type hints

```python
def munge(input: AnyStr, sep: AnyStr = None, limit=1000): ...
```
becomes:
```python
def munge(input: AnyStr, sep: AnyStr=None, limit=1000): ...
```
[From PEP 8](https://www.python.org/dev/peps/pep-0008/#other-recommendations).