I cannot confirm this.  I tested 3.6.6 on Windows 10 with tem3.py containing

import unittest
print unittest

I ran this twice, without and with debug on.  The output:

======================== RESTART: F:\Python\a\tem3.py ========================
<module 'unittest' from 'C:\\Programs\\Python36\\lib\\unittest\\__init__.py'>
>>> 
[DEBUG ON]
>>> 
======================== RESTART: F:\Python\a\tem3.py ========================
<module 'unittest' from 'C:\\Programs\\Python36\\lib\\unittest\\__init__.py'>
[DEBUG ON]
>>>

On the second run, I hit the [Go] button on Debug Control.  The minimal program above needs to be tested with 3.6.6 or 3.7.0 on Linux.