The following code works fine with python 3.7 but breaks with 3.8:

```
import dataclasses
from typing import Optional

@dataclasses.dataclass
class TestingDataclass:
    base_path: dataclasses.InitVar[Optional[str]] = None
```

Exception traceback:

```
Traceback (most recent call last):
  File "test.py", line 6, in <module>
    class TestingDataclass:
  File "/usr/local/lib/python3.8/dataclasses.py", line 995, in dataclass
    return wrap(cls)
  File "/usr/local/lib/python3.8/dataclasses.py", line 987, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
  File "/usr/local/lib/python3.8/dataclasses.py", line 967, in _process_class
    str(inspect.signature(cls)).replace(' -> None', ''))
  File "/usr/local/lib/python3.8/inspect.py", line 3050, in __str__
    formatted = str(param)
  File "/usr/local/lib/python3.8/inspect.py", line 2568, in __str__
    formatannotation(self._annotation))
  File "/usr/local/lib/python3.8/inspect.py", line 1202, in formatannotation
    return repr(annotation)
  File "/usr/local/lib/python3.8/dataclasses.py", line 213, in __repr__
    return f'dataclasses.InitVar[{self.type.__name__}]'
  File "/usr/local/lib/python3.8/typing.py", line 757, in __getattr__
    raise AttributeError(attr)
AttributeError: __name__
```

The code runs fine with `str` instead of `Optional[str]`.

Tested locally with `Python 3.8.0rc1 (tags/v3.8.0rc1:34214de6ab, Oct 10 2019, 16:15:14)`. The same error can be seen (in a more involved context) on travis [here](https://travis-ci.org/samuelcolvin/pydantic/jobs/596131963)

This is a bug with the `__repr__` method on `InitVar`.

I'm working on a PR now.

git blame points to https://github.com/python/cpython/commit/01ee12ba35a333e8a6a25c4153c4a21838e9585c . I am tagging this as a 3.8 regression since the commit was not backported and 3.7 works fine. Feel free to remove it if it's a mistake.

Oh, Samuel already made a PR. Then I withdraw PR 16701.

New changeset 793cb85437299a3da3d74fe65480d720af330cbb by Serhiy Storchaka (Samuel Colvin) in branch 'master':
bpo-38431: Fix __repr__ method of InitVar to work with typing objects. (GH-16702)
https://github.com/python/cpython/commit/793cb85437299a3da3d74fe65480d720af330cbb

New changeset 6da52ac411947d1a7958bbad831fcf8dfc8c95fe by Miss Islington (bot) in branch '3.8':
bpo-38431: Fix __repr__ method of InitVar to work with typing objects. (GH-16702)
https://github.com/python/cpython/commit/6da52ac411947d1a7958bbad831fcf8dfc8c95fe

Thank you for your contribution Samuel!