genometools: move to Python 3

Formula/genometools.rb

@@ -3,7 +3,7 @@ class Genometools < Formula
   homepage "http://genometools.org/"
   url "http://genometools.org/pub/genometools-1.5.10.tar.gz"
   sha256 "0208591333b74594bc219fb67f5a29b81bb2ab872f540c408ac1743716274e6a"
-  revision 1
+  revision 2
   head "https://github.com/genometools/genometools.git"
 
   bottle do
@@ -17,7 +17,7 @@ class Genometools < Formula
   depends_on "pkg-config" => :build
   depends_on "cairo"
   depends_on "pango"
-  depends_on "python@2"
+  depends_on "python"
 
   conflicts_with "libslax", :because => "both install `bin/gt`"
 
@@ -31,13 +31,13 @@ class Genometools < Formula
         "gtlib = CDLL(\"libgenometools\" + soext)",
         "gtlib = CDLL(\"#{lib}/libgenometools\" + soext)"
 
-      system "python", *Language::Python.setup_install_args(prefix)
-      system "python", "-m", "unittest", "discover", "tests"
+      system "python3", *Language::Python.setup_install_args(prefix)
+      system "python3", "-m", "unittest", "discover", "tests"
     end
   end
 
   test do
     system "#{bin}/gt", "-test"
-    system "python2.7", "-c", "import gt"
+    system "python3", "-c", "import gt"
   end
 end