Fixed a few imports and docs.

rtv/curses_helpers.py

@@ -3,6 +3,7 @@ import time
 import threading
 import curses
 from curses import textpad, ascii
+from contextlib import contextmanager
 
 from .docs import HELP
 from .helpers import strip_textpad
@@ -272,4 +273,4 @@ def curses_session():
             stdscr.keypad(0)
             curses.echo()
             curses.nocbreak()
-            curses.endwin()
+            curses.endwin()