It was failing because of the pre installation request from pip to ./setup.py egg_info (which is perfectly valid request and shouldn't fail), before numpy actually was installed.
Fix is straightforward - not to use numpy for commands that are not connected with build and install.
The main reason this affects me is I want to include pyastronomy into a requirements.txt file along with numpy. pip downloads and setups all before starting to install.
The main issue is https://github.com/pypa/pip/issues/25 but it is a fairly common issue.
In a new environment
Basically https://github.com/scipy/scipy/pull/453 contains the PR of how they resolved this issue for scipy which I quote.
The main reason this affects me is I want to include pyastronomy into a requirements.txt file along with numpy.
pip
downloads and setups all before starting to install.