use utf-8 encoding when parsing the BEP
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index c448409..fb7be10 100644
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -521,7 +521,7 @@
 def bes_invocation_id(bep_file):
     targets = []
     raw_data = ""
-    with open(bep_file) as f:
+    with open(bep_file, encoding="utf-8") as f:
         raw_data = f.read()
     decoder = json.JSONDecoder()