This started as a spelling and whitespace cleanup. The comment for

This started as a spelling and whitespace cleanup.  The comment for
the set_trace fiddling didn't make sense to me, and I ended up reworking
that part of the code.  We really do want to save and restore
pdb.set_trace, so that each dynamically nested level of doctest gets
sys.stdout fiddled to what's appropriate for *it*.  The only "trick"
really needed is that these layers of set_trace wrappers each call the
original pdb.set_trace (instead of the current pdb.set_trace).