openpyxl.drawing.graphicGroupTransform2D fails on instantiate

Created originally on Bitbucket by jusdino (Justin Frahm)

Instantiating a GroupTransform2D results in an exception:

from openpyxl.drawing.graphic import GroupTransform2D
gt = GroupTransform2D()

Python 3.6 stack trace:

Traceback (most recent call last):
  File "/home/jusdino/ownCloud/Documents/eclipse/openpyxl/openpyxl/descriptors/base.py", line 57, in _convert
    value = expected_type(value)
TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
 During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/home/jusdino/ownCloud/Documents/eclipse/openpyxl/openpyxl/drawing/graphic.py", line 53, in __init__
    self.rot = rot
  File "/home/jusdino/ownCloud/Documents/eclipse/openpyxl/openpyxl/descriptors/base.py", line 69, in __set__
    value = _convert(self.expected_type, value)
  File "/home/jusdino/ownCloud/Documents/eclipse/openpyxl/openpyxl/descriptors/base.py", line 59, in _convert
    raise TypeError('expected ' + str(expected_type))
TypeError: expected <class 'int'>

Python 2.7 stack trace:

Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/home/jusdino/ownCloud/Documents/eclipse/openpyxl/openpyxl/drawing/graphic.py", line 53, in __init__
    self.rot = rot
  File "/home/jusdino/ownCloud/Documents/eclipse/openpyxl/openpyxl/descriptors/base.py", line 69, in __set__
    value = _convert(self.expected_type, value)
  File "/home/jusdino/ownCloud/Documents/eclipse/openpyxl/openpyxl/descriptors/base.py", line 59, in _convert
    raise TypeError('expected ' + str(expected_type))
TypeError: expected <type 'long'>

This happens when using 2.5, 2.6, and Default branches.

Attachments: dct_clean.xlsm