File "/home/leroy/.local/lib/python3.6/site-packages/electrum/gui/qt/main_window.py", line 3084, in closeEvent
    self.clean_up()
  File "/home/leroy/.local/lib/python3.6/site-packages/electrum/gui/qt/main_window.py", line 3101, in clean_up
    self.gui_object.close_window(self)
  File "/home/leroy/.local/lib/python3.6/site-packages/electrum/gui/qt/__init__.py", line 266, in close_window
    self.daemon.stop_wallet(window.wallet.storage.path)
  File "/home/leroy/.local/lib/python3.6/site-packages/electrum/daemon.py", line 267, in stop_wallet
    wallet.stop_threads()
  File "/home/leroy/.local/lib/python3.6/site-packages/electrum/address_synchronizer.py", line 168, in stop_threads
    self.storage.write()
  File "/home/leroy/.local/lib/python3.6/site-packages/electrum/util.py", line 344, in <lambda>
    return lambda *args, **kw_args: do_profile(args, kw_args)
  File "/home/leroy/.local/lib/python3.6/site-packages/electrum/util.py", line 340, in do_profile
    o = func(*args, **kw_args)
  File "/home/leroy/.local/lib/python3.6/site-packages/electrum/storage.py", line 107, in write
    self._write()
  File "/home/leroy/.local/lib/python3.6/site-packages/electrum/storage.py", line 115, in _write
    s = json.dumps(self.data, indent=4, sort_keys=True, cls=util.MyEncoder)
  File "/usr/lib/python3.6/json/__init__.py", line 238, in dumps
    **kw).encode(obj)
  File "/usr/lib/python3.6/json/encoder.py", line 201, in encode
    chunks = list(chunks)
  File "/usr/lib/python3.6/json/encoder.py", line 430, in _iterencode
    yield from _iterencode_dict(o, _current_indent_level)
  File "/usr/lib/python3.6/json/encoder.py", line 404, in _iterencode_dict
    yield from chunks
  File "/usr/lib/python3.6/json/encoder.py", line 353, in _iterencode_dict
    items = sorted(dct.items(), key=lambda kv: kv[0])