gnu: slepc: Update to 3.16.1.

* gnu/packages/maths.scm (slepc): Update to 3.16.1.
[native-inputs]: Use PYTHON instead of PYTHON-2.  Add WHICH.
[properties]: New field.

gnu/packages/maths.scm

@@ -3112,7 +3112,7 @@ (define-public python2-kiwisolver
 (define-public slepc
   (package
     (name "slepc")
-    (version "3.11.1")
+    (version "3.16.1")
     (source
      (origin
        (method url-fetch)
@@ -3120,10 +3120,11 @@ (define-public slepc
                            version ".tar.gz"))
        (sha256
         (base32
-         "1yq84q9wannc8xwapxpay4ypdd675picwi395hhsdvng9q6hf5j8"))))
+         "1ysfm77s5fcissv3q0k5d65mlp93zi4anqg62q3cd25dn66sva5i"))))
     (build-system gnu-build-system)
     (native-inputs
-     `(("python" ,python-2)
+     `(("python" ,python)
+       ("which" ,which)
        ("petsc:examples" ,petsc "examples"))) ;for gmakegen.py script
     (inputs
      `(("arpack" ,arpack-ng)
@@ -3184,7 +3185,9 @@ (define-public slepc
 The emphasis of the software is on methods and techniques appropriate for
 problems in which the associated matrices are sparse, for example, those
 arising after the discretization of partial differential equations.")
-    (license license:bsd-2)))
+    (license license:bsd-2)
+    (properties
+     `((release-monitoring-url . "http://slepc.upv.es/download/")))))
 
 (define-public slepc-complex
   (package (inherit slepc)