Use exec_tools for TFLite generate_examples genrule

This is required for PY3 compatibility when the target is used as a tool
dependency from a genrule.

PiperOrigin-RevId: 326718880
Change-Id: I9ff432642564db9620711139351f196e782434fd

Author: jdduke

tensorflow/lite/build_def.bzl

@@ -647,7 +647,8 @@ def gen_zipped_test_file(name, file, toco, flags):
         cmd = (("$(locations :generate_examples) --toco $(locations {0}) " +
                 " --zip_to_output {1} {2} $(@D)").format(toco, file, flags)),
         outs = [file],
-        tools = [
+        # `exec_tools` is required for PY3 compatibility in place of `tools`.
+        exec_tools = [
             ":generate_examples",
             toco,
         ],

tensorflow/lite/testing/zip_test_utils.py

@@ -162,7 +162,8 @@ def format_result(t):
     values = ["{:.9f}".format(value) for value in list(t.flatten())]
     return ",".join(values)
   else:
-    return _pywrap_string_util.SerializeAsHexString(t.flatten())
+    # SerializeAsHexString returns bytes in PY3, so decode if appropriate.
+    return _pywrap_string_util.SerializeAsHexString(t.flatten()).decode("utf-8")
 
 
 def write_examples(fp, examples):