Enable Alpine portability test to run under Python 3. (#27464)

* Enable Alpine portability test to run under Python 3.

* Fix other scripts

tools/run_tests/python_utils/jobset.py

@@ -130,7 +130,7 @@ def message(tag, msg, explanatory_text=None, do_newline=False):
         try:
             if platform_string() == 'windows' or not sys.stdout.isatty():
                 if explanatory_text:
-                    logging.info(explanatory_text.decode('utf8'))
+                    logging.info(explanatory_text)
                 logging.info('%s: %s', tag, msg)
             else:
                 sys.stdout.write(
@@ -240,7 +240,7 @@ class JobResult(object):
 
 def read_from_start(f):
     f.seek(0)
-    return f.read()
+    return f.read().decode("utf8")
 
 
 class Job(object):

tools/run_tests/python_utils/upload_test_results.py

@@ -88,7 +88,7 @@ def _get_build_metadata(test_results):
 def _insert_rows_with_retries(bq, bq_table, bq_rows):
     """Insert rows to bq table. Retry on error."""
     # BigQuery sometimes fails with large uploads, so batch 1,000 rows at a time.
-    for i in range((len(bq_rows) / 1000) + 1):
+    for i in range((len(bq_rows) // 1000) + 1):
         max_retries = 3
         for attempt in range(max_retries):
             if big_query_utils.insert_rows(bq, _PROJECT_ID, _DATASET_ID,