dependencies: added required psutil for gevent.

pkgs/python-packages.nix

@@ -475,6 +475,17 b' self: super: {'
       license = [ pkgs.lib.licenses.bsdOriginal ];
     };
   };
+  "psutil" = super.buildPythonPackage {
+    name = "psutil-5.4.6";
+    doCheck = false;
+    src = fetchurl {
+      url = "https://files.pythonhosted.org/packages/51/9e/0f8f5423ce28c9109807024f7bdde776ed0b1161de20b408875de7e030c3/psutil-5.4.6.tar.gz";
+      sha256 = "1xmw4qi6hnrhw81xqzkvmsm9im7j2vkk4v26ycjwq2jczqsmlvk8";
+    };
+    meta = {
+      license = [ pkgs.lib.licenses.bsdOriginal ];
+    };
+  };
   "ptyprocess" = super.buildPythonPackage {
     name = "ptyprocess-0.6.0";
     doCheck = false;
@@ -681,6 +692,7 b' self: super: {'
       self."mercurial"
       self."msgpack-python"
       self."pastedeploy"
+      self."psutil"
       self."pyramid"
       self."pyramid-mako"
       self."pygments"

requirements.txt

@@ -13,6 +13,7 b' mercurial==4.6.1'
 msgpack-python==0.4.8
 
 pastedeploy==1.5.2
+psutil==5.4.6
 pyramid==1.9.2
 pyramid-mako==1.0.2