Removed all the mixed indentation face stuff. It's not as helpful as

it at first seems.  I think we've got a good idea of what to do, but
it'll be a bit of work... for later.

Misc/python-mode.el

@@ -309,13 +309,6 @@ source code of the innermost frame.")
   :type 'function
   :group 'python)
 
-(defface py-mixed-indentation-face nil
-  "Face that mixed indentation is displayed in.
-To quickly see mixed tabs/spaces, use \\[customize-face] and set the
-background of `py-mixed-indentation-face' to something obnoxious (like
-\"Yellow\")."
-  :group 'python)
-
 ;; Not customizable
 (defvar py-master-file nil
   "If non-nil, execute the named file instead of the buffer's file.
@@ -378,8 +371,6 @@ support for features needed by `python-mode'.")
      ;; functions
      '("\\bdef[ \t]+\\([a-zA-Z_]+[a-zA-Z0-9_]*\\)"
        1 font-lock-function-name-face)
-     ;; mixed tabs and spaces indentation
-     '("^[ \t]*\\( \t\\|\t \\)[ \t]*" 0 py-mixed-indentation-face)
      ))
   "Additional expressions to highlight in Python mode.")
 (put 'python-mode 'font-lock-defaults '(python-font-lock-keywords))