docs: def _fullCloneOrFallback(self):
          """Wrapper for _fullClone(). In the case of failure, if clobberOnFailure
             is set to True remove the build directory and try a full clone again.
          """
  
          res = yield self._fullClone()
          if res != RC_SUCCESS:
              if not self.clobberOnFailure:
                  raise buildstep.BuildStepFailed()
              res = yield self.clobber()
          return res