[Tutor] problem with creating paths

[Shall, Sydney]

Firstly, I would like to thank Steven for reminding me of the assert 
statement. I should have remembered this. It allowed me to isolate the 
problem, which predictably (for me) was very elementary. I am too 
embarrassed to say how simple the error was.

However, my original problem was not solved by correcting this error.

So, I will now try and narrow down the location of the problem and then 
if I cannot solve it, I shall return for more good advice.

Many thanks to Steven and to Peter.

Sydney