gnu: python-scikit-learn: Use OpenBLAS instead of ATLAS.

* gnu/packages/python.scm (python-scikit-learn)[inputs]: Replace "atlas" with
  "openblas".
* gnu/packages/python.scm (python-scikit-learn)[arguments]: Remove build phase
  'set-environment-variables, which is only needed when ATLAS is used.

gnu/packages/python.scm

@@ -2081,19 +2081,6 @@ sources.")
     (build-system python-build-system)
     (arguments
      `(#:phases
-       (alist-cons-before
-        'build 'set-environment-variables
-        (lambda* (#:key inputs #:allow-other-keys)
-          (let* ((atlas-threaded
-                  (string-append (assoc-ref inputs "atlas")
-                                 "/lib/libtatlas.so"))
-                 ;; On single core CPUs only the serial library is created.
-                 (atlas-lib
-                  (if (file-exists? atlas-threaded)
-                      atlas-threaded
-                      (string-append (assoc-ref inputs "atlas")
-                                     "/lib/libsatlas.so"))))
-            (setenv "ATLAS" atlas-lib)))
        (alist-cons-before
         'check 'set-HOME
         ;; some tests require access to "$HOME"
@@ -2108,9 +2095,9 @@ sources.")
              ;; (sklearn.tests.test_common.test_transformers); see
              ;; https://github.com/scikit-learn/scikit-learn/issues/3693
              (system* "nosetests" "-v" "sklearn")))
-          (alist-delete 'check %standard-phases))))))
+         (alist-delete 'check %standard-phases)))))
     (inputs
-     `(("atlas" ,atlas)
+     `(("openblas" ,openblas)
        ("python-nose" ,python-nose)))
     (propagated-inputs
      `(("python-numpy" ,python-numpy)