networkx: fixing undeclared dependency

the current version of networkx implicitly depends on
pkg_resources from setuptools to check the version of
pydot (networkx/networkx#3173).

(cherry picked from commit 5b3fb23)

pkgs/development/python-modules/networkx/default.nix

@@ -3,6 +3,7 @@
 , fetchPypi
 , nose
 , decorator
+, setuptools
 }:
 
 buildPythonPackage rec {
@@ -17,7 +18,7 @@ buildPythonPackage rec {
   };
 
   checkInputs = [ nose ];
-  propagatedBuildInputs = [ decorator ];
+  propagatedBuildInputs = [ decorator setuptools ];
 
   meta = {
     homepage = "https://networkx.github.io/";