BUG/DEPR: the deprecation of util.testing fails for direct imports
```
In [1]: from pandas.util.testing import assert_frame_equal  
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-1-79d99d902fdd> in <module>
----> 1 from pandas.util.testing import assert_frame_equal

ImportError: cannot import name 'assert_frame_equal' from 'pandas.util.testing' (/home/joris/scipy/pandas/pandas/util/testing/__init__.py)
```

It works when accessing from top-level import:

```
In [3]: pd.util.testing.assert_frame_equal
/home/joris/miniconda3/envs/dev/bin/ipython:1: FutureWarning: pandas._testing.assert_frame_equal is deprecated. Please use pandas.testing.assert_frame_equal instead.
  #!/home/joris/miniconda3/envs/dev/bin/python
Out[3]: <function pandas._testing.assert_frame_equal(left, right, check_dtype=True, check_index_type='equiv', check_column_type='equiv', check_frame_type=True, check_less_precise=False, check_names=True, by_blocks=False, check_exact=False, check_datetimelike_compat=False, check_categorical=True, check_like=False, obj='DataFrame')>
```