matplotlib and basemap require setuptools to run properly together (#3835)

* matplotlib and basemap require setuptools to run properly together

* flake 8 fix

var/spack/repos/builtin/packages/py-matplotlib/package.py

@@ -59,7 +59,10 @@ class PyMatplotlib(PythonPackage):
     extends('python', ignore=r'bin/nosetests.*$|bin/pbr$')
 
     # ------ Required dependencies
-    depends_on('py-setuptools', type='build')
+    # Per Github issue #3813, setuptools is required at runtime in order
+    # to make mpl_toolkits a namespace package that can span multiple
+    # directories (i.e., matplotlib and basemap)
+    depends_on('py-setuptools', type=('build', 'run'))
 
     depends_on('libpng@1.2:')
     depends_on('freetype@2.3:')