pil: Uninstall correctly.

Installs now into the cellar, so that uninstall works.

Closes Homebrew/homebrew#16558.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/pil.rb

@@ -46,8 +46,24 @@ class Pil < Formula
               "add_directory(include_dirs, \"#{HOMEBREW_PREFIX}/include\")"
     end
 
-    system "python", "setup.py", "build_ext"
-    system "python", "setup.py", "install", "--prefix=#{prefix}"
+    # In order to install into the Cellar, the dir must exist and be in the
+    # PYTHONPATH.
+    temp_site_packages = lib/which_python/'site-packages'
+    mkdir_p temp_site_packages
+    ENV['PYTHONPATH'] = temp_site_packages
+    args = [
+      "--no-user-cfg",
+      "--verbose",
+      "install",
+      "--force",
+      "--install-scripts=#{share}/python",
+      "--install-lib=#{temp_site_packages}",
+      "--install-data=#{share}",
+      "--install-headers=#{include}",
+      "--record=installed-files.txt"
+    ]
+    system "python", "-s", "setup.py", *args
+
   end
 
   def caveats; <<-EOS.undent
@@ -56,6 +72,10 @@ class Pil < Formula
     the build will fail.
     EOS
   end
+
+  def which_python
+    "python" + `python -c 'import sys;print(sys.version[:3])'`.strip
+  end
 end
 
 __END__