(Using CPython commit 6b1ac809b9)

This program never executes line 4, but the "if not __debug__" is partly attributed to line 4, giving an incorrect trace:

    for value in [True, False]:
        if value:
            if not __debug__:
                1/0 # line 4
        else:
            x = 6

Using a simple trace program (https://github.com/nedbat/coveragepy/blob/master/lab/run_trace.py), it produces this output:

    call <string> 1 @-1
        line <string> 1 @0
        line <string> 2 @8
        line <string> 3 @12
        line <string> 4 @14
        line <string> 1 @4
        line <string> 2 @8
        line <string> 6 @16
        line <string> 1 @4
        return <string> 1 @24

Various simplifications of the program make the problem go away.