Add python symlink to python3

BUG=b:280640695

Change-Id: I0840abae09ae2798fdfb73bfd2d28bebffe5a440
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/xolabs-common-core/+/4500893
Reviewed-by: Prasad Vuppalapu <prasadv@chromium.org>
Commit-Queue: Anh Le <anhdle@chromium.org>
Tested-by: Anh Le <anhdle@chromium.org>
diff --git a/src/dockerfiles/servod/Dockerfile b/src/dockerfiles/servod/Dockerfile
index 99e6e6a..50082fd 100644
--- a/src/dockerfiles/servod/Dockerfile
+++ b/src/dockerfiles/servod/Dockerfile
@@ -10,7 +10,8 @@
     && apt-get install -y --no-install-recommends \
         bzip2 \
         curl \
-        fdisk
+        fdisk \
+        python-is-python3
 
 # Avoid watchtower updating servod, it gets pulled before every start of the
 # container, we should not stop/start it in the case a new version is pushed.