loggerhead can't reasonably be installed using pip due to self-import in setup.py

Following the fix for bug 383360, I tried to make Launchpad install loggerhead using pip (with a self-built sdist from the breezy branch). However, this didn't work because loggerhead's setup.py does an 'import loggerhead' to get the version, and loggerhead/__init__.py does pkg_resources.get_distribution('Paste>=1.6') which fails because Paste hasn't been installed yet. That means that the declaration of dependencies is ineffective: if you want to install loggerhead using pip then you have to take care to explicitly install at least Paste first, which is cumbersome.

I think loggerhead should arrange to get its version in setup.py in a way that doesn't involve importing itself at that stage.