Tom,
took a first look with postgresql 9.2 on OpenSuse 12.3.
I get the expected failure for postgresql when adding your test function.
However adding your code changes still let me see the test failure
and I get an additional one:


FAIL: testFilteringRangeGeekInterval (test.test_postgresql.postgresqlDBTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/lib64/python2.7/unittest/case.py", line 327, in run
    testMethod()
  File "/home/bernhard/hacking/roundup/roundup-hg/./test/db_test_base.py", line 
1351, in testFilteringRangeGeekInterval
    ae(filt(None, {'deadline': '-2d;'}), ['5', '6'])
  File "/usr/lib64/python2.7/unittest/case.py", line 511, in assertEqual
    assertion_func(first, second, msg=msg)
[...]
AssertionError: Lists differ: ['6'] != ['5', '6']

First differing element 0:
6
5

Second list contains 1 additional elements.
First extra element 1:
6

- ['6']
+ ['5', '6']

Do you also see that second test failure?
I have not analysed further yet.


One hint about creating patches: Usually a unified context diff is easier to read, "-
u" option for "diff". And you can put several changes in one patch files, which 
makes it easier to apply.