code: def _crawl_elsevier_and_find_issue_xml(self):
          
          self._found_issues = []
          if not self.path and not self.package_name:
              for issue in self.conn._get_issues():
                  dirname = issue.rstrip('/issue.xml')
                  try:
                      self._normalize_issue_dir_with_dtd(dirname)
                      self._found_issues.append(dirname)
                  except Exception as err:
                      register_exception()
                      print("ERROR: can't normalize %s: %s" % (dirname, err))
          else:
              def visit(dummy, dirname, names):
                  if "issue.xml" in names:
                      try:
                          self._normalize_issue_dir_with_dtd(dirname)
                          self._found_issues.append(dirname)
                      except Exception as err:
                          register_exception()
                          print("ERROR: can't normalize %s: %s"
                                % (dirname, err))
              walk(self.path, visit, None)
docs: Information about the current volume, issue, etc. is available
          in a file called issue.xml that is available in a higher directory.