gnu: python-numpy: Update to 1.13.1.

* gnu/packages/python.scm (python-numpy, python2-numpy): Update to 1.13.1.
[source]: Download the zip release from pypi instead of a git snapshot.
[native-inputs]: Add unzip.
[arguments]: Set SHELL environment variable.

Co-authored by Leo Famulari <leo@famulari.name>

gnu/packages/python.scm

@@ -3720,22 +3720,21 @@ between language specification and implementation aspects.")
 (define-public python-numpy
   (package
     (name "python-numpy")
-    (version "1.12.0")
+    (version "1.13.1")
     (source
      (origin
        (method url-fetch)
-       (uri (string-append
-             "https://github.com/numpy/numpy/archive/v" version ".tar.gz"))
-       (file-name (string-append name "-" version ".tar.gz"))
+       (uri (pypi-uri "numpy" version ".zip"))
        (sha256
         (base32
-         "025d4j4aakcp8w5i5diqh812cbbjgac7jszx1j56ivrbi1i8vv7d"))))
+         "1fsgkhh1vdkhmlz8vmdgxnj9n9yaanckxxzz9s0b4p08fqvjic69"))))
     (build-system python-build-system)
     (inputs
      `(("openblas" ,openblas)
        ("lapack" ,lapack)))
     (native-inputs
-     `(("python-cython" ,python-cython)
+     `(("unzip" ,unzip)
+       ("python-cython" ,python-cython)
        ("python-nose" ,python-nose)
        ("gfortran" ,gfortran)))
     (arguments
@@ -3743,6 +3742,8 @@ between language specification and implementation aspects.")
        (modify-phases %standard-phases
         (add-before 'build 'set-environment-variables
          (lambda* (#:key inputs #:allow-other-keys)
+           ;; numpy's distutils uses $SHELL to run external commands.
+          (setenv "SHELL" "bash")
           (call-with-output-file "site.cfg"
             (lambda (port)
               (format port