remote client exits immediately with EOFError on input

[o-smirnov]

On hall, this input() call: https://github.com/ratt-ru/radiopadre-client/blob/master/radiopadre_client/backends/venv.py#L221

...throws an EOFError even though the connection is still open. Find a more robust way to check for closed ssh connection. SIGHUP or some such?

If I just print the exception and continue, I have this:

radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall stderr: [W 12:52:32.990 NotebookApp] Config option `template_path` not recognized by `LenvsLatexExporter`.  Did you mean one of: `extra_template_paths, template_name, template_paths`?
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: Type 'exit' to kill the session: radiopadre.client: EOF error: EOF when reading a line
radiopadre.client: hall: [2022-07-07 12:52:32.990] [info] Session 1 [127.0.0.1] Connected. Num sessions: 1
radiopadre.client: hall stderr: [W 12:52:32.993 NotebookApp] Config option `template_path` not recognized by `LenvsLatexExporter`.  Did you mean one of: `extra_template_paths, template_name, template_paths`?
radiopadre.client: hall stderr: [W 12:52:33.066 NotebookApp] Config option `template_path` not recognized by `LenvsSlidesExporter`.  ```