[WORKSPACE] Add hermetic dependency on the Python "six" package.

PiperOrigin-RevId: 197558539

README.md

@@ -150,8 +150,8 @@ software libraries, which we ship in several different ways:
      software rendering via OSMesa, depending on the `--define headless=...`
      build setting.
    * Python 2.7 (other versions might work, too) with NumPy, PIL. (A few
-     tests require a NumPy version of at least 1.8.) One test requires six
-     to demonstrate Python 3 compatibility.
+     tests require a NumPy version of at least 1.8.) Python 3 is supported
+     experimentally.
 
 The build rules are using a few compiler settings that are specific to GCC. If
 some flags are not recognized by your compiler (typically those would be

RELEASE_NOTES.md

@@ -24,6 +24,7 @@
 2.  The demo `:game` has a new flag `--start_index` to start at an episode index
     other than 0.
 3.  Add a console command `dm_pickup` to pick up an item identified by its `id`.
+4.  More Python demos and tests now work with Python 3.
 
 ## release-2018-05-15 May 2018 release
 

WORKSPACE

@@ -75,6 +75,17 @@ new_http_archive(
     ],
 )
 
+new_http_archive(
+    name = "six_archive",
+    build_file = "six.BUILD",
+    sha256 = "105f8d68616f8248e24bf0e9372ef04d3cc10104f1980f54d57b2ce73a5ad56a",
+    strip_prefix = "six-1.10.0",
+    urls = [
+        "https://mirror.bazel.build/pypi.python.org/packages/source/s/six/six-1.10.0.tar.gz",
+        "https://pypi.python.org/packages/source/s/six/six-1.10.0.tar.gz",
+    ],
+)
+
 # TODO: Replace with hermetic build
 new_local_repository(
     name = "lua_system",

python/tests/BUILD

@@ -18,6 +18,7 @@ py_test(
     data = ["//:deepmind_lab.so"],
     imports = ["python"],
     main = "dmlab_module_test.py",
+    deps = ["@six_archive//:six"],
 )
 
 py_test(

six.BUILD

@@ -0,0 +1,13 @@
+# Description:
+#   Six provides simple utilities for wrapping over differences between Python 2
+#   and Python 3.
+
+licenses(["notice"])  # MIT
+
+exports_files(["LICENSE"])
+
+py_library(
+    name = "six",
+    srcs = ["six.py"],
+    visibility = ["//visibility:public"],
+)