Move python sepolicy tests to embedded launcher

This is a necessary for enforcing these tests in CTS.

Bug: 37008075
Test: build
Change-Id: I36b4ce71c26a0ba01cd0289fe363f0a9f7db1214
(cherry picked from commit 8d614b3f8191ece8a8ce5002949a0fe54e009177)
diff --git a/tests/Android.bp b/tests/Android.bp
index 8fe89e5..8dc3330 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -19,6 +19,7 @@
     name: "py2_only",
     version: {
         py2: {
+            embedded_launcher: true,
             enabled: true,
         },
         py3: {
diff --git a/tests/policy.py b/tests/policy.py
index a0ddb90..4bc9c91 100644
--- a/tests/policy.py
+++ b/tests/policy.py
@@ -2,6 +2,7 @@
 import re
 import os
 import sys
+import platform
 
 ###
 # Check whether the regex will match a file path starting with the provided
@@ -252,12 +253,13 @@
 
     # load ctypes-ified libsepol wrapper
     def __InitLibsepolwrap(self, LibPath):
-        if "linux" in sys.platform:
+        if "linux" in platform.system().lower():
             lib = CDLL(LibPath + "/libsepolwrap.so")
-        elif "darwin" in sys.platform:
+        elif "darwin" in platform.system().lower():
             lib = CDLL(LibPath + "/libsepolwrap.dylib")
         else:
-            sys.exit("only Linux and Mac currrently supported")
+            sys.exit("policy.py: " + platform.system() + " not supported." +
+                    " Only Linux and Darwin platforms are currently supported.")
 
         # int get_allow_rule(char *out, size_t len, void *policydbp, void *avtab_iterp);
         lib.get_allow_rule.restype = c_int