[rustyline] Update to work with the latest nix.

Change-Id: I4eb5d77f6ef86a50bbd80c01160685422d68dcbf
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/rust-mirrors/rustyline/+/770742
Reviewed-by: Tyler Mandry <tmandry@google.com>
diff --git a/src/tty/unix.rs b/src/tty/unix.rs
index 4255555..00cd8c2 100644
--- a/src/tty/unix.rs
+++ b/src/tty/unix.rs
@@ -655,10 +655,9 @@
     // Interactive loop:
 
     fn enable_raw_mode(&mut self) -> Result<Mode> {
-        use nix::errno::Errno::ENOTTY;
         use nix::sys::termios::{ControlFlags, InputFlags, LocalFlags, SpecialCharacterIndices};
         if !self.stdin_isatty {
-            try!(Err(nix::Error::from_errno(ENOTTY)));
+            try!(Err(nix::Error::ENOTTY));
         }
         let original_mode = try!(termios::tcgetattr(STDIN_FILENO));
         let mut raw = original_mode.clone();