Try installing it

nixos/modules/leasereport-repo.nix

+let
+  pkgs = import <nixpkgs> {};
+in
+  pkgs.fetchFromGitHub {
+    owner = "PrivateStorageio";
+    repo = "LeaseReport";
+    rev = "59d98d2e0d14ac05e4c57b285463910e04b8a9b0";
+    sha256 = "0w5msd6q7lpfabzs3d5czcb3jbi9vdh5xzp13phjc4gimfdzfd94";
+  }
\ No newline at end of file

nixos/modules/leasereport.nix

+{ callPackage }:
+let
+  leasereport = import ./leasereport-repo.nix;
+in
+  callPackage "${leasereport}/nix" { }

nixos/modules/overlays.nix

@@ -15,6 +15,8 @@ let
   };
 in
 self: super: {
+  leasereport = self.callPackage ./leasereport.nix { };
+
   # Use self.python27 to get the fixed point of all packages (that is, to
   # respect all of the overrides).  This is important since we want the
   # overridden Twisted as a dependency of this env, not the original one.

nixos/modules/private-storage.nix

@@ -139,5 +139,10 @@ in
     [ "d ${incidents-dir} 0755 root root ${max-incident-age} -"
     ];
 
+    environment.systemPackages = [
+      # Provide a useful tool for reporting about shares.
+      pspkgs.leasereport
+    ];
+
   };
 }