bpo-33065: Fix problem debugging user classes with __repr__ method (GH-24183)

bpo-33065: Fix problem debugging user classes with __repr__ method (GH-24183)

If __repr__ uses instance attributes, as normal, and one steps
through the __init__ method, debugger may try to get repr before
the instance attributes exist.  reprlib.repr handles the error.
(cherry picked from commit 81f87bbf9f65702062021a78abd9b8f82c98a414)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>