gettz('') fails on windows

[labrys]

Given the following (tested with Python 3.7 and dateutil 2.8.0):

import dateutil.tz
print(dateutil.tz.gettz(''))

On Linux:

None

On Windows:

Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "H:\src\env\desc\lib\site-packages\dateutil\tz\tz.py", line 1551, in __call__
    rv = self.nocache(name=name)
  File "H:\src\env\desc\lib\site-packages\dateutil\tz\tz.py", line 1635, in nocache
    tz = tzwin(name)
  File "H:\src\env\desc\lib\site-packages\dateutil\tz\win.py", line 223, in __init__
    self._std_abbr = keydict["Std"]
KeyError: 'Std'