whitedb: rename python@2 optional dependency

Formula/whitedb.rb

@@ -14,14 +14,16 @@ class Whitedb < Formula
     sha256 "aa86b2acca68b9999ecb4cb9da7c64f659a97ffbd50d7aeb78c021df13866474" => :mountain_lion
   end
 
-  depends_on "python" => :optional
+  deprecated_option "with-python" => "with-python@2"
+
+  depends_on "python@2" => :optional
 
   def install
     # https://github.com/priitj/whitedb/issues/15
     ENV.append "CFLAGS", "-std=gnu89"
 
     args = ["--prefix=#{prefix}"]
-    args << "--with-python" if build.with? "python"
+    args << "--with-python" if build.with? "python@2"
     system "./configure", *args
 
     system "make"