add ocolor as a dependency

.nix/catala.nix

@@ -25,6 +25,7 @@
 , zarith_stubs_js
 , ocaml-crunch
 , cohttp-lwt-unix
+, ocolor
 }:
 
 buildDunePackage {
@@ -62,6 +63,7 @@ buildDunePackage {
     zarith
     zarith_stubs_js
     cohttp-lwt-unix
+    ocolor
   ];
 
   # Currently there is no unit tests in catala and Cram tests are handled by clerk

.nix/ocolor.nix

@@ -0,0 +1,39 @@
+{ lib
+, buildDunePackage
+, odoc
+, cppo
+, ounit
+, fetchurl
+}:
+
+buildDunePackage rec {
+  pname = "ocolor";
+  version = "1.3.0";
+  
+  minimumOCamlVersion = "4.11";
+
+  src = fetchurl
+    {
+      url = "https://github.com/marc-chevalier/${pname}/archive/${version}.tar.gz";
+      sha256 = "sha256-V7xuBRNbWWi3OpDRe7WakOO4Vz6nyoV8/gyn45fpmYA=";
+    };
+
+  duneVersion = "3";
+
+  propagatedBuildInputs = [
+    odoc
+    ounit
+    cppo
+  ];
+
+  nativeBuildInputs = [ cppo ];
+  doCheck = true;
+
+  meta = with lib; {
+    homepage = "https://github.com/marc-chevalier/ocolor";
+    description =
+      "OColor is an OCaml library which help to format nicely using ANSI escape codes.";
+    license = licenses.mit;
+    maintainers = [ ];
+  };
+}

.nix/packages.nix

@@ -11,4 +11,5 @@ ocamlPackages.overrideScope' (self: super: {
   ubase = self.callPackage ./ubase.nix { };
   dates_calc = self.callPackage ./dates_calc.nix { };
   french_law = self.callPackage ./french_law.nix { };
+  ocolor = self.callPackage ./ocolor.nix { };
 })