- looks like around python3.9, they changed it so that
if we don't block on the main thread, it starts to shut things down
- polling thread.join() makes Ctrl+C work. kind of.
```
$ ./electrum/scripts/txradar.py 6bde84a981e72573666fcc51c81ec3f8f4a813709bf16451dce3f106a114d392
Exception in run: RuntimeError('cannot schedule new futures after interpreter shutdown')
Traceback (most recent call last):
File "/home/user/wspace/electrum/electrum/util.py", line 1218, in wrapper
return await func(*args, **kwargs)
File "/home/user/wspace/electrum/electrum/interface.py", line 649, in wrapper_func
return await func(self, *args, **kwargs)
File "/home/user/wspace/electrum/electrum/interface.py", line 675, in run
await self.open_session(ssl_context=ssl_context)
File "/home/user/wspace/electrum/electrum/interface.py", line 872, in open_session
async with _RSClient(
File "/home/user/.local/lib/python3.10/site-packages/aiorpcx/rawsocket.py", line 167, in __aenter__
_transport, protocol = await self.create_connection()
File "/home/user/wspace/electrum/electrum/interface.py", line 285, in create_connection
return await super().create_connection()
File "/home/user/.local/lib/python3.10/site-packages/aiorpcx/rawsocket.py", line 163, in create_connection
return await connector.create_connection(
File "/usr/lib/python3.10/asyncio/base_events.py", line 1036, in create_connection
infos = await self._ensure_resolved(
File "/usr/lib/python3.10/asyncio/base_events.py", line 1418, in _ensure_resolved
return await loop.getaddrinfo(host, port, family=family, type=type,
File "/usr/lib/python3.10/asyncio/base_events.py", line 863, in getaddrinfo
return await self.run_in_executor(
File "/usr/lib/python3.10/asyncio/base_events.py", line 821, in run_in_executor
executor.submit(func, *args), loop=self)
File "/usr/lib/python3.10/concurrent/futures/thread.py", line 169, in submit
raise RuntimeError('cannot schedule new futures after '
RuntimeError: cannot schedule new futures after interpreter shutdown
```
Note: this was causing a weird flake8 error on CI. Presumably due to CI running flake8 via py3.7.
```
flake8 . --count --select=$ELECTRUM_LINTERS --show-source --statistics
./electrum/scripts/update_default_servers.py:1:26: E999 SyntaxError: invalid syntax
#!/usr/bin/env python3
^
1 E999 SyntaxError: invalid syntax
1
```
