Fix ModuleNotFoundError: No module named 'pandas.formats'
Fixes `test_shim` failure:
```
================================== FAILURES ===================================
__________________________________ test_shim __________________________________

    def test_shim():
        # https://github.com/pandas-dev/pandas/pull/16059
        # Remove in 0.21
        with tm.assert_produces_warning(FutureWarning,
                                        check_stacklevel=False):
>           from pandas.formats.style import Styler as _styler  # noqa
E           ModuleNotFoundError: No module named 'pandas.formats'

X:\Python36\lib\site-packages\pandas\tests\io\formats\test_style.py:866: ModuleNotFoundError
```