Readline history bug

[A]

The readline package doesn't return the errno for some errors in write_history, 
append_history, and history_truncate_file.
This caused an error in the CPython interpreter(at exit time) when the 
.python_history file was not writable.

In particular these calls return -1 when the internal`histfile_restore`call 
fails because`rename`fails. It's fine for`histfile_restore`to return the result 
from`rename`, but this should be checked for failure (e.g. -1) and handled 
appropriately by the caller in`history_do_write`and`history_truncate_file`. For 
example, in`history_do_write`they do the following:

if (rv == 0 && histname && tempname)
    rv = histfile_restore (tempname, histname);

if (rv != 0)
    {
      if (tempname)
        unlink (tempname);
      history_lines_written_to_file = 0;
    }

This needs a simple fix to update the value of`rv`when`histfile_restore`fails:

if (rv == 0 && histname && tempname)
    rv = histfile_restore (tempname, histname);

if (rv != 0) {
    rv = errno;
    if (tempname)
        unlink(tempname);
    history_lines_written_to_file = 0;
}

Code snippet taken from 
https://github.com/python/cpython/pull/18299#issuecomment-580883515

publickey - auroralanes@protonmail.ch - 0x72D037C6.asc
Description: application/pgp-keys

signature.asc
Description: OpenPGP digital signature