We've hit a problem in the Tahoe packaging scheme: we kind of want to use the setuptools install_requires= feature to declare that Tahoe depends upon Twisted (as well as other things). This allows someone to type "easy_install allmydata-tahoe" and get everything built for them. It also allows our build process to download and build anything that the user doesn't already have on their system, making the build process much easier. The trouble that we've run into is that various flavors of linux have made different decisions about which setuptools "distribution" names to use. (Note that these "distribution names" are the name= arguments to setup(), as opposed to the python package names like or module names. Distribution names tend to map to debian package names.) http://allmydata.org/trac/tahoe/ticket/378 has more details, but basically Ubuntu is shipping .egg_info data that declares that the "Twisted" distribution is installed, whereas debian sid is shipping data that says "Twisted-Core" is installed. Since the setuptools dependency syntax is not rich enough to provide alternatives, the Tahoe setup.py is forced to choose between depending upon "Twisted" or upon "Twisted-Core". The drawback for choosing the opposite of the target platform is that users on that platform will find their tahoe builds downloading and building the whole Twisted-8.0.1 tarball, despite having a perfectly functional twisted-2.5.0 installation already present. This is annoying. We haven't figured out a good resolution to this problem yet. The best answer I can think of would be to change the tahoe setup.py script to change the dependencies that it declares based upon what is currently installed. This would be a bit wonky but might avoid spurious download+builds. Another answer might be for the debian 'python-twisted' metapackage (which depends upon python-twisted-core, python-twisted-web, etc) to provide an .egg-info that claims to represent the 'Twisted' distribution, but I can imagine problems with that. Another possibility would be for the Ubuntu python-twisted-core package to install two .egg-info files, the one for 'Twisted' that they're already doing, and another for 'Twisted-Core'.. if that were the case, we could have Tahoe depend upon 'Twisted-Core ' and 'Twisted-Web' and be done with it. So, no answers, but we're bringing up the issue in case anyone else has run into a similar problem, or has some bright ideas on the subject. cheers, -Brian