gnu: ams-lv2: Fix error in configure phase.

Python 3.7 introduced PEP 479. That raised an error in an old waf-script
included in the package. An updated waf-script was found in a
newer commit that fixes the problem.

* gnu/packages/music.scm (ams-lv2)[sources]: Update, using two more commits
than version 1.2.1.

gnu/packages/music.scm

@@ -18,6 +18,7 @@
 ;;; Copyright © 2018 Stefan Reichör <stefan@xsteve.at>
 ;;; Copyright © 2018 Pierre Neidhardt <mail@ambrevar.xyz>
 ;;; Copyright © 2018 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2018 Björn Höfling <bjoern.hoefling@bjoernhoefling.de>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -2285,47 +2286,52 @@ follows a traditional multi-track tape recorder control paradigm.")
     (license license:gpl2+)))
 
 (define-public ams-lv2
-  (package
+  ;; Version 1.2.1 built with Python 3.7 raises an error in the waf-script.
-    (name "ams-lv2")
+  ;; Therefore, we take two more commmits than 1.2.1 that introduce an updated
-    (version "1.2.1")
+  ;; waf-script and fix one error.
-    (source
+  (let ((commit "377d166db54a787b48979171c5652d2eb4f1bbb5")
-     (origin
+        (revision "1"))
-       (method git-fetch)
+    (package
-       (uri (git-reference
+      (name "ams-lv2")
-             (url "https://github.com/blablack/ams-lv2.git")
+      (version (git-version "1.2.1" revision commit))
-             (commit version)))
+      (source
-       (file-name (git-file-name name version))
+       (origin
-       (sha256
+         (method git-fetch)
-        (base32
+         (uri (git-reference
-         "1n1dnqnj24xhiy9323lj52nswr5120cj56fpckg802miss05sr6x"))))
+               (url "https://github.com/blablack/ams-lv2.git")
-    (build-system waf-build-system)
+               (commit commit)))
-    (arguments
+         (file-name (git-file-name name version))
-     `(#:phases
+         (sha256
-       (modify-phases %standard-phases
+          (base32
-         (add-after 'unpack 'remove-sse-flags
+           "1ndgxcxjxwidg7436k0nb5clxkyi878k1j999sbbd1gk2fm0kcqm"))))
-           (lambda* (#:key system #:allow-other-keys)
+      (build-system waf-build-system)
-             (when (not (or (string-prefix? "x86_64" system)
+      (arguments
-                            (string-prefix? "i686" system)))
+       `(#:phases
-               (substitute* "wscript"
+         (modify-phases %standard-phases
-                 (("'-msse', '-mfpmath=sse', ") ""))
+           (add-after 'unpack 'remove-sse-flags
-             #t))))
+             (lambda* (#:key system #:allow-other-keys)
-       #:tests? #f)) ; no tests
+               (when (not (or (string-prefix? "x86_64" system)
-    (inputs
+                              (string-prefix? "i686" system)))
-     `(("lv2" ,lv2)
+                     (substitute* "wscript"
-       ("lvtk" ,lvtk)
+                       (("'-msse', '-mfpmath=sse', ") ""))
-       ("gtkmm" ,gtkmm-2)
+                     #t))))
-       ("gtk" ,gtk+-2)
+         #:tests? #f)) ; no tests
-       ("cairo" ,cairo)
+      (inputs
-       ("fftw" ,fftw)))
+       `(("lv2" ,lv2)
-    (native-inputs
+         ("lvtk" ,lvtk)
-     `(("pkg-config" ,pkg-config)))
+         ("gtkmm" ,gtkmm-2)
-    (home-page "https://objectivewave.wordpress.com/ams-lv2/")
+         ("gtk" ,gtk+-2)
-    (synopsis "Port of Alsa Modular Synth internal modules into LV2")
+         ("cairo" ,cairo)
-    (description "This set of LV2 plugins is a port of the internal modules
+         ("fftw" ,fftw)))
+      (native-inputs
+       `(("pkg-config" ,pkg-config)))
+      (home-page "https://objectivewave.wordpress.com/ams-lv2/")
+      (synopsis "Port of Alsa Modular Synth internal modules into LV2")
+      (description "This set of LV2 plugins is a port of the internal modules
 found in Alsa Modular Synth.  These plugins are used to create modular
 synthesizers and contain: VCO, VCF, VCA, LFO, slew limiter, envelopes, sample
 and hold, etc.")
-    (license license:gpl2)))
+      (license license:gpl2))))
 
 (define-public gxtuner
   (package