File "electrum/gui/qt/network_dialog.py", line 468, in set_server
  File "electrum/network.py", line 299, 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 934, in wrapper
  File "electrum/network.py", line 617, in set_parameters
  File "electrum/network.py", line 635, in switch_lagging_interface
  File "electrum/blockchain.py", line 186, in func_wrapper
  File "electrum/blockchain.py", line 462, in read_header