miniterm: Python 3 fix for cancel, fixes #137
diff --git a/serial/tools/miniterm.py b/serial/tools/miniterm.py
index 145996f..016183e 100644
--- a/serial/tools/miniterm.py
+++ b/serial/tools/miniterm.py
@@ -169,7 +169,7 @@
             return c
 
         def cancel(self):
-            os.write(self.pipe_w, "x")
+            os.write(self.pipe_w, b"x")
 
         def cleanup(self):
             termios.tcsetattr(self.fd, termios.TCSAFLUSH, self.old)