protobuf: depend on six

This switches `protobuf` to depend on `six` as a formula instead of as a
resource.

See #73875.

Formula/protobuf.rb

@@ -4,6 +4,7 @@ class Protobuf < Formula
   url "https://github.com/protocolbuffers/protobuf/releases/download/v3.17.0/protobuf-all-3.17.0.tar.gz"
   sha256 "96da1cb0648c7c1b2e68ef7089149dce18ecf8d0582a171315b3991a59e629c6"
   license "BSD-3-Clause"
+  revision 1
 
   livecheck do
     url :stable
@@ -26,11 +27,7 @@ class Protobuf < Formula
   end
 
   depends_on "python@3.9" => [:build, :test]
-
+  depends_on "six"
-  resource "six" do
-    url "https://files.pythonhosted.org/packages/71/39/171f1c67cd00715f190ba0b100d606d440a28c93c7714febeca8b79af85e/six-1.16.0.tar.gz"
-    sha256 "1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926"
-  end
 
   def install
     # Don't build in debug mode. See:
@@ -53,18 +50,10 @@ class Protobuf < Formula
     ENV.append_to_cflags "-I#{include}"
     ENV.append_to_cflags "-L#{lib}"
 
-    resource("six").stage do
-      system Formula["python@3.9"].opt_bin/"python3", *Language::Python.setup_install_args(libexec)
-    end
     chdir "python" do
-      system Formula["python@3.9"].opt_bin/"python3", *Language::Python.setup_install_args(libexec),
+      system Formula["python@3.9"].opt_bin/"python3", *Language::Python.setup_install_args(prefix),
                         "--cpp_implementation"
     end
-
-    version = Language::Python.major_minor_version Formula["python@3.9"].opt_bin/"python3"
-    site_packages = "lib/python#{version}/site-packages"
-    pth_contents = "import site; site.addsitedir('#{libexec/site_packages}')\n"
-    (prefix/site_packages/"homebrew-protobuf.pth").write pth_contents
   end
 
   test do

pypi_formula_mappings.json

@@ -88,6 +88,9 @@
   "poetry": {
     "extra_packages": ["importlib-metadata", "typing-extensions"]
   },
+  "protobuf": {
+    "exclude_packages": ["six"]
+  },
   "regipy": {
     "exclude_packages": ["tabulate"]
   },