The missing file ("_rpatool.py") is dynamically created right before it is called, and it is effectively created, else you would have another error message (something about an exception occurring during the call of "ReadAllText"). So I assume that, for some unknown reason, it is created somewhere else.
It can be, without guaranties, because "c:\Users\[YOU]\Desktop" isn't at all intended for this. If really you want it in "c:\Users\[YOU]", put it in "c:\Users\[YOU]\Documents" (that can have another name with the same meaning in your localized version of Windows).