Sfaely flush thread on buffer

news/rediralias.rst

@@ -12,5 +12,6 @@
   the function ProcProxies were not being waited upon.
 * Fixed issue with callablable aliases that happen to call sys.exit() or
   raise SystemExit taking out the whole xonsh process.
+* Safely flushes file handles on threaded buffers.
 
 **Security:** None

xonsh/proc.py

@@ -795,7 +795,7 @@ class FileThreadDispatcher:
 
     def flush(self):
         """Flushes the file descriptor for the current thread."""
-        return self.handle.flush()
+        return safe_flush(self.handle)
 
     def isatty(self):
         """Returns if the file descriptor for the current thread is a tty."""