Provide better summaries of Retry OOPS's

[James Henstridge]

We occasionally get Retry exceptions in the OOPS summaries. These are reported similar to:

Retry: (<class psycopg.ProgrammingError at 0x2aaaaeebe050>, <psycopg.ProgrammingError instance at 0x2aaadcba9368>, <traceback object at 0x2aaadcba9638>)

To help debug these problems, it would be useful to see the details of the wrapped exception/traceback, and include them in the OOPS report.

This could either be done specific to Retry exceptions, or we could try and detect wrapped exceptions with something like:
  if len(value.args) == 3 and issubclass(value.args[0], Exception) and isinstance(value.args[2], traceback):
      ...

The additional traceback could just be appended after the first traceback in the OOPS report.