docs: def _printTraceback(self, test, err):
          """Print a nicely formatted traceback.
  
          :arg err: exc_info()-style traceback triple
          :arg test: the test that precipitated this call
  
          """
          # Don't bind third item to a local var; that can create
          # circular refs which are expensive to collect. See the
          # sys.exc_info() docs.
          exception_type, exception_value = err[:2]
          # TODO: In Python 3, the traceback is attached to the exception
          # instance through the __traceback__ attribute. If the instance
          # is saved in a local variable that persists outside the except
          # block, the traceback will create a reference cycle with the
          # current frame and its dictionary of local variables. This will
          # delay reclaiming dead resources until the next cyclic garbage
          # collection pass.
  
          extracted_tb = extract_relevant_tb(
              err[2],
              exception_type,
              exception_type is test.failureException)
          test_frame_index = index_of_test_frame(
              extracted_tb,
              exception_type,
              exception_value,
              test)
          if test_frame_index:
              # We have a good guess at which frame is the test, so
              # trim everything until that. We don't care to see test
              # framework frames.
              extracted_tb = extracted_tb[test_frame_index:]
  
          with self.bar.dodging():
              self.stream.write(''.join(
                  format_traceback(
                      extracted_tb,
                      exception_type,
                      exception_value,
                      self._cwd,
                      self._term,
                      self._options.function_color,
                      self._options.dim_color,
                      self._options.editor,
                      self._options.editor_shortcut_template)))