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/gconv_strip.py b/scripts/gconv_strip.py
index 836d417..6729b32 100644
--- a/scripts/gconv_strip.py
+++ b/scripts/gconv_strip.py
@@ -85,7 +85,7 @@
 
     def Load(self):
         """Load the charsets from gconv-modules."""
-        with open(self._filename) as fp:
+        with open(self._filename, encoding="utf-8") as fp:
             for line in fp:
                 line = line.split("#", 1)[0].strip()
                 if not line:
@@ -204,7 +204,7 @@
 
         # Recompute the gconv-modules file with only the included gconv modules.
         result = []
-        with open(self._filename) as fp:
+        with open(self._filename, encoding="utf-8") as fp:
             for line in fp:
                 lst = line.split("#", 1)[0].strip().split()