File "electrum\gui\qt\history_list.py", line 594, in create_menu
  File "electrum\wallet.py", line 853, in cpfp
  File "electrum\wallet.py", line 155, in get_locktime_for_new_transaction
  File "electrum\blockchain.py", line 432, in header_at_tip
  File "electrum\blockchain.py", line 182, in func_wrapper
  File "electrum\blockchain.py", line 419, in read_header
  File "electrum\blockchain.py", line 381, in assert_headers_file_available