Added fileno() method to StdoutProxy.

Author: jonathanslenders

prompt_toolkit/patch_stdout.py

@@ -143,3 +143,10 @@ def flush(self):
  """
  with self._lock:
  self._flush()
+
+ def fileno(self):
+ """
+ Return file descriptor.
+ """
+ # This is important for code that expects sys.stdout.fileno() to work.
+ return self.original_stdout.fileno()