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/cros_generate_deps_graphs.py b/scripts/cros_generate_deps_graphs.py
index e6ed511..14e37e7 100644
--- a/scripts/cros_generate_deps_graphs.py
+++ b/scripts/cros_generate_deps_graphs.py
@@ -173,5 +173,5 @@
         GenerateImages(sys.stdin.read(), options)
     else:
         for i in options.inputs:
-            with open(i) as handle:
+            with open(i, encoding="utf-8") as handle:
                 GenerateImages(handle.read(), options)