Prevent Python from importing the host's pip packages

This patch prevents Python from searching the user's installed pip
packages as well as the host's `site` package. The host's `site`
package normally performs the setup necessary to allow importing
globally installed pip packages. We don't want that.

From the upstream documentation:
https://docs.python.org/3/using/cmdline.html

    -s
        Don’t add the user site-packages directory to sys.path.
        See also PEP 370 – Per user site-packages directory

    -S
        Disable the import of the module site and the
        site-dependent manipulations of sys.path that it
        entails. Also disable these manipulations if site is
        explicitly imported later (call site.main() if you
        want them to be triggered).

Change-Id: I11a64c33920fc174dd8ac5d200e2e8550a3c084a
Signed-off-by: Philipp Schrader <philipp.schrader@gmail.com>
diff --git a/y2020/vision/tools/python_code/BUILD b/y2020/vision/tools/python_code/BUILD
index 1e27f65..7579a75 100644
--- a/y2020/vision/tools/python_code/BUILD
+++ b/y2020/vision/tools/python_code/BUILD
@@ -4,12 +4,10 @@
 py_library(
     name = "train_and_match",
     srcs = ["train_and_match.py"],
-    data = [
-        "@python_repo//:scipy",
-    ],
     deps = [
         "//external:python-glog",
         "@opencv_contrib_nonfree_amd64//:python_opencv",
+        "@python_repo//:scipy",
     ],
 )
 
@@ -18,13 +16,11 @@
     srcs = [
         "define_training_data.py",
     ],
-    data = [
-        "@python_repo//:scipy",
-    ],
     deps = [
         ":train_and_match",
         "//external:python-glog",
         "@opencv_contrib_nonfree_amd64//:python_opencv",
+        "@python_repo//:scipy",
     ],
 )