Update uf2 tools to support python3.

tannewt · tannewt · commit 70df242f724c · 2018-07-25T09:39:46.000-07:00
diff --git a/tools/uf2 b/tools/uf2
@@ -1 +1 @@
-Subproject commit 6c37e72342d814079bc9b760e2840dc0d766f94f
+Subproject commit 968716efd30600984139d706bcbd8ec1a1b2336d
