Add a python-wrapped opencv, complete with SIFT support

Change-Id: I06cd05a8974670fb886123ef24e4c44c2a985362
diff --git a/build_tests/python_opencv.py b/build_tests/python_opencv.py
new file mode 100644
index 0000000..c353c79
--- /dev/null
+++ b/build_tests/python_opencv.py
@@ -0,0 +1,6 @@
+#!/usr/bin/python3
+
+import cv2
+
+if __name__ == '__main__':
+  cv2.xfeatures2d.SIFT_create()