acloud: import six for compatibility between py2 and py3.

Add py-six into Androip.bp and provide simple utilities for wrapping over differences between py2 and py3.

BUG:137195528
Test: atest acloud_test --host
Change-Id: If187e6d567890a46b0b841229e5f6a6df419bffb
diff --git a/Android.bp b/Android.bp
index 3ff0421..fb9f40e 100644
--- a/Android.bp
+++ b/Android.bp
@@ -55,7 +55,8 @@
         "py-dateutil",
         "py-google-api-python-client",
         "py-oauth2client",
-	"py-pyopenssl",
+        "py-pyopenssl",
+        "py-six",
     ],
     dist: {
         targets: ["droidcore"],