code: def db_set_indexing(cls, is_indexing, impl, working_dir):
          
          indexing_lockfile_path = config.get_lockfile_filename(impl, working_dir)
          if is_indexing:
              # make sure this exists
              with open(indexing_lockfile_path, 'w') as f:
                  pass
  
          else:
              # make sure it does not exist 
              try:
                  os.unlink(indexing_lockfile_path)
              except:
                  pass
docs: Set lockfile path as to whether or not the system is indexing.
          NOT THREAD SAFE, USE ONLY FOR CRASH DETECTION.