python3: only apply xcode-stubs patch for stable (#1500)

* python3: only apply xcode-stubs.diff on stable

Closes #1499.

* python3: use #{pkgshare} to eliminate audit error

Formula/python3.rb

@@ -1,8 +1,21 @@
 class Python3 < Formula
   desc "Interpreted, interactive, object-oriented programming language"
   homepage "https://www.python.org/"
-  url "https://www.python.org/ftp/python/3.5.1/Python-3.5.1.tar.xz"
-  sha256 "c6d57c0c366d9060ab6c0cdf889ebf3d92711d466cc0119c441dbf2746f725c9"
+
+  head "https://hg.python.org/cpython", :using => :hg
+
+  stable do
+    url "https://www.python.org/ftp/python/3.5.1/Python-3.5.1.tar.xz"
+    sha256 "c6d57c0c366d9060ab6c0cdf889ebf3d92711d466cc0119c441dbf2746f725c9"
+
+    # Fix extension module builds against Xcode 7 SDKs
+    # https://github.com/Homebrew/homebrew/issues/41085
+    # https://bugs.python.org/issue25136
+    patch do
+      url "https://bugs.python.org/file40478/xcode-stubs.diff"
+      sha256 "029cc0dc72b1bcf4ddc5f913cc4a3fd970378073c6355921891f041aca2f8b12"
+    end
+  end
 
   bottle do
     revision 3
@@ -11,8 +24,6 @@ class Python3 < Formula
     sha256 "228380b8fb1ed6f496c6b071443ecdf98b1130aa840a4e2bd9ccae3dc7bb2713" => :mavericks
   end
 
-  head "https://hg.python.org/cpython", :using => :hg
-
   option :universal
   option "with-tcl-tk", "Use Homebrew's Tk instead of OS X Tk (has optional Cocoa and threads support)"
   option "with-quicktest", "Run `make quicktest` after the build"
@@ -57,14 +68,6 @@ class Python3 < Formula
   # X11.
   patch :DATA if build.with? "tcl-tk"
 
-  # Fix extension module builds against Xcode 7 SDKs
-  # https://github.com/Homebrew/homebrew/issues/41085
-  # https://bugs.python.org/issue25136
-  patch do
-    url "https://bugs.python.org/file40478/xcode-stubs.diff"
-    sha256 "029cc0dc72b1bcf4ddc5f913cc4a3fd970378073c6355921891f041aca2f8b12"
-  end
-
   def lib_cellar
     prefix/"Frameworks/Python.framework/Versions/#{xy}/lib/python#{xy}"
   end
@@ -175,7 +178,7 @@ def install
     # Tell Python not to install into /Applications (default for framework builds)
     system "make", "install", "PYTHONAPPSDIR=#{prefix}"
     # Demos and Tools
-    system "make", "frameworkinstallextras", "PYTHONAPPSDIR=#{share}/python3"
+    system "make", "frameworkinstallextras", "PYTHONAPPSDIR=#{pkgshare}"
     system "make", "quicktest" if build.with? "quicktest"
 
     # Any .app get a " 3" attached, so it does not conflict with python 2.x.