Hack around Zlib constant conflict

Library/Homebrew/utils.rb

@@ -305,7 +305,7 @@ module GitHub extend self
     # This is a no-op if the user is opting out of using the GitHub API.
     return if ENV['HOMEBREW_NO_GITHUB_API']
 
-    require 'net/https' # for exception classes below
+    safely_load_net_https
 
     default_headers = {
       "User-Agent" => HOMEBREW_USER_AGENT,
@@ -402,4 +402,24 @@ module GitHub extend self
     uri = URI.parse("https://api.github.com/repos/#{user}/#{repo}")
     open(uri) { |json| json["private"] }
   end
+
+  private
+
+  # If the zlib formula is loaded, TypeError will be raised when we try to load
+  # net/https. This monkeypatch prevents that and lets Net::HTTP fall back to
+  # the non-gzip codepath.
+  def safely_load_net_https
+    return if defined?(Net::HTTP)
+    if defined?(Zlib) && RUBY_VERSION >= "1.9"
+      require "net/protocol"
+      http = Class.new(Net::Protocol) do
+        def self.require(lib)
+          raise LoadError if lib == "zlib"
+          super
+        end
+      end
+      Net.const_set(:HTTP, http)
+    end
+    require "net/https"
+  end
 end