launchpadlib tests requires python 2.6

While building the installer for 2.4b2/OSX 10.5 I encoutered the following:

byte-compiling /Users/vila/src/mac-installers/trunk/package/launchpadlib.dst/Library/Python/2.5/site-packages/launchpadlib/tests/test_credential_store.py to test_credential_store.pyc
/Library/Python/2.5/site-packages/launchpadlib/tests/test_credential_store.py:93: Warning: 'with' will become a reserved keyword in Python 2.6
  File "/Library/Python/2.5/site-packages/launchpadlib/tests/test_credential_store.py", line 93
    with fake_keyring(self.keyring):
                    ^
SyntaxError: invalid syntax

byte-compiling /Users/vila/src/mac-installers/trunk/package/launchpadlib.dst/Library/Python/2.5/site-packages/launchpadlib/tests/test_http.py to test_http.pyc
byte-compiling /Users/vila/src/mac-installers/trunk/package/launchpadlib.dst/Library/Python/2.5/site-packages/launchpadlib/tests/test_launchpad.py to test_launchpad.pyc
/Library/Python/2.5/site-packages/launchpadlib/tests/test_launchpad.py:521: Warning: 'with' will become a reserved keyword in Python 2.6
  File "/Library/Python/2.5/site-packages/launchpadlib/tests/test_launchpad.py", line 521
    with warnings.catch_warnings(record=True) as caught:
                ^
SyntaxError: invalid syntax

This is not a big deal since this only means that the installer can't run the tests for launchpadlib but it's still a bit worrying.

Possible options include:
- design and carry a patch for launchpadlib (I doubt upstream will be interested),
- drop launchpadlib from the installer (ouch, some plugins depend on it so they will probably need to be dropped as well),
- stop building the installer for 10.5,
- switch to python-2.6 for OSX 10.5 (this will requires asking users to install python from python.org)