For development, the "install everything locally" that virtual env provides. This avoids conflicting, incompatible versions of packages being installed in a glo

For development, the "install everything locally" that virtual env provides. This avoids conflicting, incompatible versions of packages being installed in a global or per-user location. Python isn't at all the only language to suffer this problem. e.g. "DLL hell" and its variations like Haskell's "cabal hell". With Ruby, if its packages are installed with bundler, then these packages are installed locally in the project directory.