Customer asked me to look at a 2.5 based project yesterday. No problem, just fire up my virtualenv and take a quick look. Hrm, no, the virtualenv isn't working... Python 2.5 isn't installed. Hrm, and it's not in the apt repository for Natty. Hrm... okay, build from source... fail on sqlite... debug... patch... build succeeds. Hrm... altinstall succeeds, but no zlib module... debug... rebuild... debug... rebuild... blah just seems broken, no non-trivial software will install. PPA of a backport... nope, not working, apt failures and a partially hosed apt (conflicts and all sorts of nasty issues).
2 un-billable hours trying to get a Python 2.5 install up, wound up having to use an old Debian machine with 2.5 installed (one of the customer's as it happens). Seems I need to get a Python 2.5 virtual machine built. 3.x doesn't matter for my business, despite my having it available on all of my current machines; no one has ever asked for it. But not being able to run Python 2.5 (which customers actually want to use, and likey will for a few years) is costing me money.