diff --git a/pkgs/python-packages.nix b/pkgs/python-packages.nix
--- a/pkgs/python-packages.nix
+++ b/pkgs/python-packages.nix
@@ -525,17 +525,6 @@ self: super: {
       license = [ { fullName = "GNU Lesser General Public License v3 or later (LGPLv3+)"; } { fullName = "LGPL"; } ];
     };
   };
-  "graphviz" = super.buildPythonPackage {
-    name = "graphviz-0.9";
-    doCheck = false;
-    src = fetchurl {
-      url = "https://files.pythonhosted.org/packages/2b/e6/71521bab8fb99833133f08f6ac0460e2f6b425a7f75ac4b02323c3c3b512/graphviz-0.9.zip";
-      sha256 = "14r9brj4r31b3qy1nnn34v3l4h0n39bqxg9sn2fz4p3pp5mglnl6";
-    };
-    meta = {
-      license = [ pkgs.lib.licenses.mit ];
-    };
-  };
   "greenlet" = super.buildPythonPackage {
     name = "greenlet-0.4.15";
     doCheck = false;
@@ -922,20 +911,6 @@ self: super: {
       license = [ pkgs.lib.licenses.bsdOriginal ];
     };
   };
-  "objgraph" = super.buildPythonPackage {
-    name = "objgraph-3.1.1";
-    doCheck = false;
-    propagatedBuildInputs = [
-      self."graphviz"
-    ];
-    src = fetchurl {
-      url = "https://files.pythonhosted.org/packages/be/58/9ca81a20cc837054e94866df1475d899caaa94f3732b8a46006858b015f7/objgraph-3.1.1.tar.gz";
-      sha256 = "17aq4cwainiwvj8x61j0hx45c313bkwza5fijnmmw8v8glyy2bcc";
-    };
-    meta = {
-      license = [ pkgs.lib.licenses.mit ];
-    };
-  };
   "packaging" = super.buildPythonPackage {
     name = "packaging-15.2";
     doCheck = false;
@@ -1696,7 +1671,6 @@ self: super: {
       self."mysql-python"
       self."pymysql"
       self."pyotp"
-      self."objgraph"
       self."packaging"
       self."paste"
       self."pastedeploy"
diff --git a/requirements.txt b/requirements.txt
--- a/requirements.txt
+++ b/requirements.txt
@@ -40,7 +40,6 @@ msgpack-python==0.5.6
 mysql-python==1.2.5
 pymysql==0.8.1
 pyotp==2.2.6
-objgraph==3.1.1
 packaging==15.2
 paste==2.0.3
 pastedeploy==1.5.2
@@ -131,3 +130,6 @@ appenlight-client==0.6.25
 
 ## test related requirements
 -r requirements_test.txt
+
+## uncomment to add the debug libraries
+#-r requirements_debug.txt
diff --git a/requirements_debug.txt b/requirements_debug.txt
new file mode 100644
--- /dev/null
+++ b/requirements_debug.txt
@@ -0,0 +1,3 @@
+## special libraries we could extend the requirements.txt file with to add some
+## custom libraries usefull for debug and memory tracing
+objgraph==3.1.1