File "electrum\gui\qt\network_dialog.py", line 459, in set_server
  File "electrum\network.py", line 287, in run_from_another_thread
  File "concurrent\futures\_base.py", line 432, in result
  File "concurrent\futures\_base.py", line 384, in __get_result
  File "electrum\util.py", line 910, in wrapper
  File "electrum\network.py", line 578, in set_parameters
  File "electrum\network.py", line 596, in switch_lagging_interface
  File "electrum\blockchain.py", line 182, in func_wrapper
  File "electrum\blockchain.py", line 419, in read_header
  File "electrum\blockchain.py", line 383, in assert_headers_file_available