workaround if someone runs in KeyError: 0 when installing from a tarball

[Reimar Bauer]

I got this issue today on one system, it will be solved

https://github.com/conda/conda/issues/2970#issuecomment-230151680

if you can't directly build a new env with our tarball try it the other way

conda create -n mssdev python=2

and afterwards build from that activated env I get the package installed

conda build .

[Reimar Bauer]

solved by a newer conda version