File "/tmp/.mount_electrXE9ljY/usr/lib/python3.7/site-packages/electrum/gui/qt/main_window.py", line 1571, in do_pay
    self.wallet.save_invoice(invoice)
  File "/tmp/.mount_electrXE9ljY/usr/lib/python3.7/site-packages/electrum/wallet.py", line 730, in save_invoice
    self.save_db()
  File "/tmp/.mount_electrXE9ljY/usr/lib/python3.7/site-packages/electrum/wallet.py", line 288, in save_db
    self.db.write(self.storage)
  File "/tmp/.mount_electrXE9ljY/usr/lib/python3.7/site-packages/electrum/wallet_db.py", line 1216, in write
    self._write(storage)
  File "/tmp/.mount_electrXE9ljY/usr/lib/python3.7/site-packages/electrum/wallet_db.py", line 1224, in _write
    storage.write(self.dump())
  File "/tmp/.mount_electrXE9ljY/usr/lib/python3.7/site-packages/electrum/util.py", line 390, in <lambda>
    return lambda *args, **kw_args: do_profile(args, kw_args)
  File "/tmp/.mount_electrXE9ljY/usr/lib/python3.7/site-packages/electrum/util.py", line 386, in do_profile
    o = func(*args, **kw_args)
  File "/tmp/.mount_electrXE9ljY/usr/lib/python3.7/site-packages/electrum/storage.py", line 104, in write
    f.write(s)