>return MyInstance
>
>in your _init_ file?
>

In turned out that this all worked once I followed Andrew's instruction to
set
FIX_TRAILING_SLASH = 1 in the configuration file.  Seems obvious once it's
pointed out that there is a setting called FIX_TRAILING_SLASH.  What I don't
really understand is why Quixote can find functions in the current namespace
that don't have a trailing slash in the URL but can't find in the current
namespace a non-callable instance's _q_index method unless there is a
trailing slash in the URL.