pandas does not import with cpython master
#### Code Sample, a copy-pastable example if possible

```python
# Your code here
import pandas
```
#### Problem description

```
jupiter@21:38  ➤  ipython                                                                                                                                                                                                                                                       
Python 3.9.0a4+ (heads/master:87ec86c425, Mar 16 2020, 11:05:13) 
Type 'copyright', 'credits' or 'license' for more information
IPython 8.0.0.dev -- An enhanced Interactive Python. Type '?' for help.

In [1]: import pandas                                                                                                                                                                                                                                                           
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-1-38d4b0363d82> in <module>
----> 1 import pandas

~/.virtualenvs/bleeding/lib/python3.9/site-packages/pandas/__init__.py in <module>
    120 from pandas.tseries.api import infer_freq
    121 from pandas.tseries import offsets
--> 123 from pandas.core.computation.api import eval
    125 from pandas.core.reshape.api import (
    126     concat,
    127     lreshape,
   (...)
    138     qcut,
    139 )
    141 import pandas.api

~/.virtualenvs/bleeding/lib/python3.9/site-packages/pandas/core/computation/api.py in <module>
      1 # flake8: noqa
----> 3 from pandas.core.computation.eval import eval

~/.virtualenvs/bleeding/lib/python3.9/site-packages/pandas/core/computation/eval.py in <module>
     11 from pandas.util._validators import validate_bool_kwarg
     13 from pandas.core.computation.engines import _engines
---> 14 from pandas.core.computation.expr import Expr, _parsers
     15 from pandas.core.computation.parsing import tokenize_string
     16 from pandas.core.computation.scope import ensure_scope

~/.virtualenvs/bleeding/lib/python3.9/site-packages/pandas/core/computation/expr.py in <module>
    188 _expr_nodes = _filter_nodes(ast.expr)
    189 _expr_context_nodes = _filter_nodes(ast.expr_context)
--> 190 _slice_nodes = _filter_nodes(ast.slice)
    191 _boolop_nodes = _filter_nodes(ast.boolop)
    192 _operator_nodes = _filter_nodes(ast.operator)

AttributeError: module 'ast' has no attribute 'slice'

In [2]:   
```

```
jupiter@21:41  ➤  git describe                                                                                      
v1.1.0.dev0-846-g7aa3dd274     
```

It looks like this is due to https://github.com/python/cpython/pull/9605 / https://bugs.python.org/issue34822 and needs to be sorted for py39
