Tobias,
I've simplified your warning case further, maybe it helps:
$ python
Python 2.5.2 (r252:60911, Jan  4 2009, 17:40:26)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from intrange import makefilter, ExpressionError
>>> makefilter("<8 and or >1")
Exception exceptions.RuntimeError: 'generator ignored GeneratorExit' in 
<generator object at 0xb7db2fec> ignored
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "workbench/numbers/intrange.py", line 235, in makefilter
    expr, varname = expressify(s)
  File "workbench/numbers/intrange.py", line 188, in expressify
    for newtype, token in completed(s):
  File "workbench/numbers/intrange.py", line 146, in completed
    % (token, newtype))
intrange.ExpressionError: 2nd token of same type (or, 2)
>>>