Holding of the __init__.py during 'make_package' cause failure on exit (Windows + IronPython)

[wenoptics]

The creation of the 'init.py' not close the file in time. This cause failure on deleting the temp folder on exit:
prelude.py#L27

Traceback (most recent call last):
  File "D:/project/example.py", line 65, in <module>
  File "C:\Program Files\IronPython 2.7\Lib\contextlib.py", line 35, in __exit__
  File "D:/project/example.py", line 14, in __stickytape_temporary_dir
  File "C:\Program Files\IronPython 2.7\Lib\shutil.py", line 261, in rmtree
  File "C:\Program Files\IronPython 2.7\Lib\shutil.py", line 266, in rmtree
  File "C:\Program Files\IronPython 2.7\Lib\shutil.py", line 240, in onerror
  File "C:\Program Files\IronPython 2.7\Lib\shutil.py", line 264, in rmtree
WindowsError: [Errno 13] The process cannot access the file because it is being used by another process

The following changes (prelude.py) work for me:

                ...
                if not os.path.exists(partial_path):
                    os.mkdir(partial_path)
                    # open(os.path.join(partial_path, "__init__.py"), "w").write("\n")
                    with open(os.path.join(partial_path, "__init__.py"), "w") as f:
                        f.write("\n")