Unable to delete last column on Windows
*Created originally on Bitbucket by [osnownoy (Andrew Kisel)](https://bitbucket.org/%7B550949da-9d13-43af-887b-9b9c94a52402%7D/)*
Today I noticed some weird issue that for some reason last column in my file (and any test file I created with similar structure) is not being deleted with 'delete_cols()'. Any other column is deleted fine. The files I tested on Windows were created on Windows machines.
Code that I used for testing on both Windows and Mac:
```
#!python
wb = openpyxl.load_workbook('Test_data.xlsx')
ws = wb.active
ws.delete_cols(5)
wb.save('Test.xlsx')
```
On Windows it simply does not change anything and on Mac it removes any column just fine.
I use Python 3.6.3 on Windows and Python 3.6.2 on Mac.
*Attachments:* [File_After_Mac](/uploads/e7c1b65956298b17251b0ef18d625f75/File_After_Mac.png)[File_Before_Mac](/uploads/72653f3aadffb5b80e1020a1745bee17/File_Before_Mac.png)
issue