scripts: update open calls to use explicit encoding

BUG=b:187789896
TEST=`cros lint` is clean here

Change-Id: Ia54475869c17292505537334362cd4cff6438b14
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4290041
Commit-Queue: Cindy Lin <xcl@google.com>
Reviewed-by: Cindy Lin <xcl@google.com>
Tested-by: Mike Frysinger <vapier@chromium.org>
Auto-Submit: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/dep_tracker.py b/scripts/dep_tracker.py
index 4ef05c8..9923b7a 100644
--- a/scripts/dep_tracker.py
+++ b/scripts/dep_tracker.py
@@ -148,7 +148,8 @@
             "files": self._files,
             "ebuilds": self._ebuilds,
         }
-        json.dump(data, open(filename, "w"))
+        with open(filename, "w", encoding="utf-8") as f:
+            json.dump(data, f)
 
     def ComputeEbuildDeps(self, sysroot):
         """Compute the dependencies between ebuilds and files.