devpi-postgresql==0.1.1 was released this morning and was throwing 500s when trying to render on both https://pypi.python.org/pypi/devpi-postgresql/0.1.1 as well as https://pypi.org/project/devpi-postgresql/0.1.1

Investigation showed that the issue is being caused by an empty string in the specifier field for a project_url type dependency:

=> select * from release_dependencies where specifier='' and name="devpi-postgresql";
name      | devpi-postgresql
version   | 0.1.1
kind      | 8
specifier | 
id        | 670291c1-74fe-4500-906e-376439f33b09

Nothing stands out in the setup.py at devpi/devpi@b54c65c#diff-8a6f387167cc787557161cb96aad255e

@fschulze: can you specifiy what tools and versions you used to package and release devpi-postgresql==0.1.1?

I note that there is another example of an empty specifier from August... see: https://gist.github.com/anonymous/f88f6b767ade67baf8b89a2d0a2e3890