Makefile
move repo attribute constants to a separate module
make REPO.SERVE_* attributes distinct from other attributes (username, password)
Merge branch 'feature/move-repo-attribute-constants-to-separate-module' into develop
generate_password()
NullRepo
Network.get_attribute("undefined-repo")
repos without type attributes are NullRepos
Merge branch 'feature/null-repo' into develop
class util.PyPI
DirectoryRepo.serve fix + tests
help for command serve
Revert "make REPO.SERVE_* attributes distinct from other attributes (username, password)"

This reverts commit 1553f4bae5f315666fac5ad9f6600ba8b076a84b.
comment for USERNAME and SERVE_USERNAME being the same
Merge branch 'feature/pypi_server' into develop