Using "modify" rather than "repair" fixed the launcher issue, a pity about this.

py
Python 3.5.1 (v3.5.1:37a07cee5969, Dec  6 2015, 01:54:25) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import tkinter
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named 'tkinter'
>>>

I only selected launcher as that was the only thing I expected to be modified.  However the modify also took an age as I recall seeing loads of stuff about test files.  You might gather that I'm extremely confused about the entire process, so exactly what is going on here?