py3: fix handling of ctrl keys in crecord (issue6213)

The "keypressed" value in handlekeypressed() is a key name obtained by
curses's getkey(); this can be a multibyte string for special keys
like CTRL keys. Calling curses.unctrl() with such a value fails on
Python 3 with a TypeError as described in issue6213. (On Python 2, this
does not crash, but I'm not sure the result is correct, though it does
no matter here.)

So instead of calling unctrl(), we compare "keypressed" with the
expected "^L" obtained by curses.ascii.ctrl("L").

mercurial/crecord.py

@@ -59,6 +59,7 b' patchhelptext = _('
 
 try:
     import curses
+    import curses.ascii
 
     curses.error
 except ImportError:
@@ -1938,7 +1939,7 b' are you sure you want to review/edit and'
             self.helpwindow()
             self.stdscr.clear()
             self.stdscr.refresh()
-        elif curses.unctrl(keypressed) in ["^L"]:
+        elif keypressed in [curses.ascii.ctrl("L")]:
             # scroll the current line to the top of the screen, and redraw
             # everything
             self.scrolllines(self.selecteditemstartline)