Two failures in 0.22.0 test__get_dtype on s390x
s390x is a big endian, so sometimes such failures (like the first one with the date) point to actual generic problems in the code which otherwise not tested... the end failure seems possibly to be something is copied without preserving the type correctly?
so thought to share:

```
___________________ test__get_dtype[input_param17-result17] ____________________

input_param = DatetimeIndex(['1970-01-01 00:00:00.000000001', '1970-01-01 00:00:00.000000002'], dtype='datetime64[ns]', freq=None)
result = dtype('<M8[ns]')

    @pytest.mark.parametrize('input_param,result', [
        (int, np.dtype(int)),
        ('int32', np.dtype('int32')),
        (float, np.dtype(float)),
        ('float64', np.dtype('float64')),
        (np.dtype('float64'), np.dtype('float64')),
        (str, np.dtype(str)),
        (pd.Series([1, 2], dtype=np.dtype('int16')), np.dtype('int16')),
        (pd.Series(['a', 'b']), np.dtype(object)),
        (pd.Index([1, 2]), np.dtype('int64')),
        (pd.Index(['a', 'b']), np.dtype(object)),
        ('category', 'category'),
        (pd.Categorical(['a', 'b']).dtype, CategoricalDtype(['a', 'b'])),
        (pd.Categorical(['a', 'b']), CategoricalDtype(['a', 'b'])),
        (pd.CategoricalIndex(['a', 'b']).dtype, CategoricalDtype(['a', 'b'])),
        (pd.CategoricalIndex(['a', 'b']), CategoricalDtype(['a', 'b'])),
        (CategoricalDtype(), CategoricalDtype()),
        (CategoricalDtype(['a', 'b']), CategoricalDtype()),
        (pd.DatetimeIndex([1, 2]), np.dtype('<M8[ns]')),
        (pd.DatetimeIndex([1, 2]).dtype, np.dtype('<M8[ns]')),
        ('<M8[ns]', np.dtype('<M8[ns]')),
        ('datetime64[ns, Europe/London]', DatetimeTZDtype('ns', 'Europe/London')),
        (pd.SparseSeries([1, 2], dtype='int32'), np.dtype('int32')),
        (pd.SparseSeries([1, 2], dtype='int32').dtype, np.dtype('int32')),
        (PeriodDtype(freq='D'), PeriodDtype(freq='D')),
        ('period[D]', PeriodDtype(freq='D')),
        (IntervalDtype(), IntervalDtype()),
    ])
    def test__get_dtype(input_param, result):
>       assert com._get_dtype(input_param) == result
E       AssertionError: assert dtype('>M8[ns]') == dtype('<M8[ns]')
E        +  where dtype('>M8[ns]') = <function _get_dtype at 0x3ff968702e8>(DatetimeIndex(['1970-01-01 00:00:00.000000001', '1970-01-01 00:00:00.000000002'], dtype='datetime64[ns]', freq=None))
E        +    where <function _get_dtype at 0x3ff968702e8> = com._get_dtype

../debian/tmp/usr/lib/python2.7/dist-packages/pandas/tests/dtypes/test_common.py:565: AssertionError
___________________ test__get_dtype[input_param18-result18] ____________________

input_param = dtype('>M8[ns]'), result = dtype('<M8[ns]')

    @pytest.mark.parametrize('input_param,result', [
        (int, np.dtype(int)),
        ('int32', np.dtype('int32')),
        (float, np.dtype(float)),
        ('float64', np.dtype('float64')),
        (np.dtype('float64'), np.dtype('float64')),
        (str, np.dtype(str)),
        (pd.Series([1, 2], dtype=np.dtype('int16')), np.dtype('int16')),
        (pd.Series(['a', 'b']), np.dtype(object)),
        (pd.Index([1, 2]), np.dtype('int64')),
        (pd.Index(['a', 'b']), np.dtype(object)),
        ('category', 'category'),
        (pd.Categorical(['a', 'b']).dtype, CategoricalDtype(['a', 'b'])),
        (pd.Categorical(['a', 'b']), CategoricalDtype(['a', 'b'])),
        (pd.CategoricalIndex(['a', 'b']).dtype, CategoricalDtype(['a', 'b'])),
        (pd.CategoricalIndex(['a', 'b']), CategoricalDtype(['a', 'b'])),
        (CategoricalDtype(), CategoricalDtype()),
        (CategoricalDtype(['a', 'b']), CategoricalDtype()),
        (pd.DatetimeIndex([1, 2]), np.dtype('<M8[ns]')),
        (pd.DatetimeIndex([1, 2]).dtype, np.dtype('<M8[ns]')),
        ('<M8[ns]', np.dtype('<M8[ns]')),
        ('datetime64[ns, Europe/London]', DatetimeTZDtype('ns', 'Europe/London')),
        (pd.SparseSeries([1, 2], dtype='int32'), np.dtype('int32')),
        (pd.SparseSeries([1, 2], dtype='int32').dtype, np.dtype('int32')),
        (PeriodDtype(freq='D'), PeriodDtype(freq='D')),
        ('period[D]', PeriodDtype(freq='D')),
        (IntervalDtype(), IntervalDtype()),
    ])
    def test__get_dtype(input_param, result):
>       assert com._get_dtype(input_param) == result
E       AssertionError: assert dtype('>M8[ns]') == dtype('<M8[ns]')
E        +  where dtype('>M8[ns]') = <function _get_dtype at 0x3ff968702e8>(dtype('>M8[ns]'))
E        +    where <function _get_dtype at 0x3ff968702e8> = com._get_dtype

../debian/tmp/usr/lib/python2.7/dist-packages/pandas/tests/dtypes/test_common.py:565: AssertionError
```
full log: https://buildd.debian.org/status/fetch.php?pkg=pandas&arch=s390x&ver=0.22.0-2&stamp=1519360704&raw=0

I will meanwhile prepare a session on one such box to be able to troubleshoot it