File "site-packages\electrum-3.1.3-py3.5.egg\electrum_gui\qt\transaction_dialog.py", line 196, in save
  File "site-packages\electrum-3.1.3-py3.5.egg\electrum_gui\qt\main_window.py", line 3185, in save_transaction_into_wallet
  File "site-packages\electrum-3.1.3-py3.5.egg\electrum\util.py", line 294, in <lambda>
  File "site-packages\electrum-3.1.3-py3.5.egg\electrum\util.py", line 290, in do_profile
  File "site-packages\electrum-3.1.3-py3.5.egg\electrum\wallet.py", line 291, in save_transactions
  File "site-packages\electrum-3.1.3-py3.5.egg\electrum\util.py", line 294, in <lambda>
  File "site-packages\electrum-3.1.3-py3.5.egg\electrum\util.py", line 290, in do_profile
  File "site-packages\electrum-3.1.3-py3.5.egg\electrum\storage.py", line 243, in write
  File "site-packages\electrum-3.1.3-py3.5.egg\electrum\storage.py", line 251, in _write
  File "json\__init__.py", line 237, in dumps
  File "json\encoder.py", line 200, in encode
  File "json\encoder.py", line 429, in _iterencode
  File "json\encoder.py", line 403, in _iterencode_dict
  File "json\encoder.py", line 352, in _iterencode_dict