STY: isort tests/scalar, tests/tslibs, import libwindow instead of _window
Ignore flake8 code "S001: found modulo formatter" which incorrectly picks up _all_ `%` characters, i.e. gives false-positives on actual mod ops.
Hello @jbrockmendel! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/window.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/core/window.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/interval/test_interval.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/interval/test_interval.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/period/test_asfreq.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/period/test_asfreq.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/period/test_period.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/period/test_period.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/test_nat.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/test_nat.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/timedelta/test_arithmetic.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/timedelta/test_arithmetic.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/timedelta/test_construction.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/timedelta/test_construction.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/timedelta/test_timedelta.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/timedelta/test_timedelta.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/timestamp/test_arithmetic.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/timestamp/test_arithmetic.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/timestamp/test_comparisons.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/timestamp/test_comparisons.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/timestamp/test_rendering.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/timestamp/test_rendering.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/timestamp/test_timestamp.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/timestamp/test_timestamp.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/timestamp/test_timezones.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/timestamp/test_timezones.py) !

 - There are no PEP8 issues in the file [`pandas/tests/scalar/timestamp/test_unary_ops.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/scalar/timestamp/test_unary_ops.py) !

 - There are no PEP8 issues in the file [`pandas/tests/tslibs/test_array_to_datetime.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/tslibs/test_array_to_datetime.py) !

 - There are no PEP8 issues in the file [`pandas/tests/tslibs/test_conversion.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/tslibs/test_conversion.py) !

 - There are no PEP8 issues in the file [`pandas/tests/tslibs/test_libfrequencies.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/tslibs/test_libfrequencies.py) !

 - There are no PEP8 issues in the file [`pandas/tests/tslibs/test_parsing.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/tslibs/test_parsing.py) !

 - There are no PEP8 issues in the file [`pandas/tests/tslibs/test_period_asfreq.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/tslibs/test_period_asfreq.py) !

 - There are no PEP8 issues in the file [`pandas/tests/tslibs/test_timezones.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/tslibs/test_timezones.py) !

 - There are no PEP8 issues in the file [`pandas/tests/tslibs/test_tslib.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tests/tslibs/test_tslib.py) !

 - There are no PEP8 issues in the file [`pandas/tseries/converter.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tseries/converter.py) !

 - There are no PEP8 issues in the file [`pandas/tseries/frequencies.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tseries/frequencies.py) !

 - There are no PEP8 issues in the file [`pandas/tseries/holiday.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tseries/holiday.py) !

 - There are no PEP8 issues in the file [`pandas/tseries/offsets.py`](https://github.com/jbrockmendel/pandas/blob/71a5fe706dbd4094ed5063c92cbb8c7fce68d413/pandas/tseries/offsets.py) !

 Travis fail is the test_rank segfault thanks!