Contrail installation fails with priority

[sureshkvl]

I am trying to installl all contrail in one VM.

analytics modules fails to install with error
/nix/store/kyjic54dlpadpi297gx2slszb79zkir3-contrail-control-5.0/lib/libsandeshvns.a' have the same priority 5;
Logs:

cloud@ocata:~/nixpkgs-tungsten$ ./please install contrail50.vrouterAgent
[please]: Running "nix-env -f default.nix -iA contrail50.vrouterAgent"

installing 'contrail-vrouter-agent-5.0'
building '/nix/store/xb50sc8a38i0z7sd4x9b94r7b3987y0z-user-environment.drv'...
error: packages '/nix/store/r1abm9nl01qjz9rdfpvcbf9dagh9a8kr-contrail-vrouter-agent-5.0/lib/libsandeshvns.a' and '/nix/store/b1wjp1lxpd3407l260hqpfi27787b31w-contrail-query-engine-5.0/lib/libsandeshvns.a' have the same priority 5; use 'nix-env --set-flag priority NUMBER INSTALLED_PKGNAME' to change the priority of one of the conflicting packages (0 being the highest priority)
builder for '/nix/store/xb50sc8a38i0z7sd4x9b94r7b3987y0z-user-environment.drv' failed with exit code 1
error: build of '/nix/store/xb50sc8a38i0z7sd4x9b94r7b3987y0z-user-environment.drv' failed
cloud@ocata:~/nixpkgs-tungsten$

[nlewo]

The goal of the install command is to create an environment with containing softwares. In this case, there is a conflict between two softwares becasue they are using the same kind of files. So Nix doesn't know which one to choose, and I don't know much more than Nix!
To run these components, you don't need to install them: you can use their absolute path to run them. The Nix way would be to generate systemd unit files for instance (with ExecStart pointing to the binary real path).