value is a list...

[NeQuissimus]

I just checked out the repo and tried to run nixpkgs-monitor --all.

I am getting this error and simply cannot figure out what is going on :)

error: while querying the derivation named ‘TPTP-6.4.0’:
value is a list while a string was expected
ERROR: Error: nixpkgs evaluation failed
/nix/store/kw2qh032jpk4cvaa7d3k5xk9g4k8nrkr-nixpkgs-monitor-dev/lib/nixpkgs_monitor/distro_packages/nix.rb:156:in `generate_list': nixpkgs evaluation failed (RuntimeError)
        from /nix/store/kw2qh032jpk4cvaa7d3k5xk9g4k8nrkr-nixpkgs-monitor-dev/bin/.nixpkgs-monitor-wrapped:151:in `block in <main>'
        from /nix/store/hlwi31crvqz9p0q4yxbmm4gv33ixpi83-ruby-1.9.3-p551/lib/ruby/1.9.1/set.rb:222:in `block in each'
        from /nix/store/hlwi31crvqz9p0q4yxbmm4gv33ixpi83-ruby-1.9.3-p551/lib/ruby/1.9.1/set.rb:222:in `each_key'
        from /nix/store/hlwi31crvqz9p0q4yxbmm4gv33ixpi83-ruby-1.9.3-p551/lib/ruby/1.9.1/set.rb:222:in `each'
        from /nix/store/kw2qh032jpk4cvaa7d3k5xk9g4k8nrkr-nixpkgs-monitor-dev/bin/.nixpkgs-monitor-wrapped:149:in `<main>'

The error is raised in nix.rb here: (I added the --show-trace)

pkgs_xml = Nokogiri.XML(%x(nix-env -qa '*' --attr-path --meta --xml --out-path --drv-path --file ./nixpkgs/ --show-trace))
raise "nixpkgs evaluation failed" unless $? == 0

To me (not knowing anything about Ruby), it seems that this is just a call to an XML library. But the output suggests that the actual error comes from a Nix expression. Running nix-env -qa '*' --attr-path --meta --xml --out-path --drv-path --file ./nixpkgs/ --show-trace directly raises no errors.