pebble-sdk: don't depend on :python.

Use the system Python instead.

Formula/pebble-sdk.rb

@@ -12,7 +12,6 @@ class PebbleSdk < Formula
   end
 
   depends_on :macos => :mountain_lion
-  depends_on :python
   depends_on 'freetype' => :recommended
   depends_on 'mpfr' => :build
   depends_on 'gmp' => :build
@@ -74,6 +73,7 @@ class PebbleSdk < Formula
       s.gsub! /^process = subprocess\.Popen\(args, shell=False, env=local_python_env\)/, "process = subprocess.Popen(args, shell=False)"
     end
 
+    ENV["PYTHONPATH"] = lib+"python2.7/site-packages"
     ENV.prepend_create_path 'PYTHONPATH', libexec+'lib/python2.7/site-packages'
     install_args = [ "setup.py", "install", "--prefix=#{libexec}" ]