To set python verbose, you can simply use -v option.

python -v

But how to do it in zope environment? This does not work:

bin/instance fg -v

So to make it work, just edit the first line in executable script, example in bin/instance

#!/home/user/buildout/foo.package/bin/python -v

Of course works with other scripts like bin/test, etc…

Now you can get more debug info when needed!