File "electrum/gui/qt/network_dialog.py", line 394, in set_server
  File "electrum/network.py", line 358, in run_from_another_thread
  File "concurrent/futures/_base.py", line 435, in result
  File "concurrent/futures/_base.py", line 384, in __get_result
  File "electrum/util.py", line 1037, in wrapper
  File "electrum/network.py", line 613, in set_parameters
  File "electrum/network.py", line 632, in switch_lagging_interface
  File "electrum/blockchain.py", line 486, in header_at_tip
  File "electrum/blockchain.py", line 201, in func_wrapper
  File "electrum/blockchain.py", line 478, in read_header