Merge pull request #8970 from soltanmm-google/profit-driven-education-seems-like-a-pretty-obvious-echo-chamber-spiral-now-that-I-think-about-it

Fix test runner failures for Python on Windows

tools/run_tests/run_tests.py

@@ -435,8 +435,8 @@ class PythonLanguage(object):
     return [self.config.job_spec(
         config.run,
         timeout_seconds=5*60,
-        environ=dict(environment.items() +
-                     [('GRPC_PYTHON_TESTRUNNER_FILTER', suite_name)]),
+        environ=dict(list(environment.items()) +
+                     [('GRPC_PYTHON_TESTRUNNER_FILTER', str(suite_name))]),
         shortname='%s.test.%s' % (config.name, suite_name),)
         for suite_name in tests_json
         for config in self.pythons]