jupyter-rendering: add celery patch, to support dateutil change

required for jupyter.

pkgs/patch-celery-dateutil.diff

@@ -0,0 +1,12 b''
+diff -rup celery-2.2.10-orig/setup.py celery-2.2.10/setup.py
+--- celery-2.2.10-orig/setup.py	2017-02-25 15:30:34.000000000 +0100
++++ celery-2.2.10/setup.py	2017-02-25 15:30:34.000000000 +0100
+@@ -48,7 +48,7 @@ try:
+ except ImportError:
+     install_requires.append("importlib")
+ install_requires.extend([
+-    "python-dateutil>=1.5.0,<2.0.0",
++    "python-dateutil>=1.5.0,<2.2.0",
+     "anyjson>=0.3.1",
+     "kombu>=1.1.2,<2.0.0",
+     "pyparsing>=1.5.0,<2.0.0",

pkgs/python-packages-overrides.nix

@@ -61,6 +61,14 b' self: super: {'
     ];
   });
 
+  celery = super.celery.override (attrs: {
+    # The current version of kombu needs some patching to work with the
+    # other libs. Should be removed once we update celery and kombu.
+    patches = [
+      ./patch-celery-dateutil.diff
+    ];
+  });
+
   kombu = super.kombu.override (attrs: {
     # The current version of kombu needs some patching to work with the
     # other libs. Should be removed once we update celery and kombu.