indetation problem

[Fuming Wang]

I am experiencing indentation problems when mixing tabs and spaces in
my code. They appear in correct indentation in my editor, but cause
error when running them. I am using Python 2.2a1. I reproduced the
problem in following interactive sequence:

>>> def dummy():
... <  tab >a = 1
... <sp><sp>b = 2
  File "<stdin>", Line 3

IndentationError: unindent does not match any outer indentation level.

Question: is this something new, or it has always been there. It is
strange that I have been using Python for several years, but only
notice this behavior recently.

Thanks,

Fuming Wang