There is no bug in the 4.3 version set; you need to fix the version conflict. Try any or all of the following approaches to this very-common problem:
(1) Remove the already-downloaded version and re-run Buildout e.g.:
$ rm -rf eggs/zc.recipe.egg\*
$ bin/buildout
(2) Remove the installed config and re-run Buildout e.g.:
$ rm .installed.cfg
$ bin/buildout
(3) Specify the version you want to use in your local config e.g.
[versions]
zc.recipe.egg = 2.0.0