gnu: python-matplotlib: Use 'modify-phases' syntax.

* gnu/packages/python.scm (python-matplotlib)[arguments]: Use 'modify-phases'.

gnu/packages/python.scm

@@ -3723,8 +3723,8 @@ transcendental functions).")
        ("texinfo" ,texinfo)))
     (arguments
      `(#:phases
-       (alist-cons-before
-        'build 'configure-environment
+       (modify-phases %standard-phases
+         (add-before 'build 'configure-environment
            (lambda* (#:key outputs inputs #:allow-other-keys)
              (let ((cairo (assoc-ref inputs "cairo"))
                    (gtk+ (assoc-ref inputs "gtk+")))
@@ -3740,9 +3740,8 @@ basedirlist = ~a,~a~%
  [rc_options]~%
 backend = TkAgg~%"
                            (assoc-ref inputs "tcl")
-                        (assoc-ref inputs "tk"))))))
-        (alist-cons-after
-         'install 'install-doc
+                           (assoc-ref inputs "tk")))))))
+         (add-after 'install 'install-doc
            (lambda* (#:key inputs outputs #:allow-other-keys)
              (let* ((data (string-append (assoc-ref outputs "doc") "/share"))
                     (doc (string-append data "/doc/" ,name "-" ,version))
@@ -3777,8 +3776,7 @@ backend = TkAgg~%"
                  (copy-file "build/texinfo/matplotlib.info"
                             (string-append info "/matplotlib.info"))
                  (copy-file "build/latex/Matplotlib.pdf"
-                          (string-append doc "/Matplotlib.pdf")))))
-        %standard-phases))))
+                            (string-append doc "/Matplotlib.pdf")))))))))
     (home-page "http://matplotlib.org")
     (synopsis "2D plotting library for Python")
     (description