run python interop tests with python3.7

tools/dockerfile/interoptest/grpc_interop_python/build_interop.sh

@@ -28,5 +28,5 @@ cp -r /var/local/jenkins/service_account $HOME || true
 
 cd /var/local/git/grpc
 
-# interop tests only run using python3.4 currently (and python build is slow)
-tools/run_tests/run_tests.py -l python --compiler python3.4 -c opt --build_only
+# interop tests only run using python3.7 currently (and python build is slow)
+tools/run_tests/run_tests.py -l python --compiler python3.7 -c opt --build_only

tools/run_tests/run_interop_tests.py

@@ -545,13 +545,13 @@ class PythonLanguage:
 
     def client_cmd(self, args):
         return [
-            'py34_native/bin/python', 'src/python/grpcio_tests/setup.py',
+            'py37_native/bin/python', 'src/python/grpcio_tests/setup.py',
             'run_interop', '--client', '--args="{}"'.format(' '.join(args))
         ]
 
     def client_cmd_http2interop(self, args):
         return [
-            'py34_native/bin/python',
+            'py37_native/bin/python',
             'src/python/grpcio_tests/tests/http2/negative_http2_client.py',
         ] + args
 
@@ -560,7 +560,7 @@ class PythonLanguage:
 
     def server_cmd(self, args):
         return [
-            'py34_native/bin/python', 'src/python/grpcio_tests/setup.py',
+            'py37_native/bin/python', 'src/python/grpcio_tests/setup.py',
             'run_interop', '--server', '--args="{}"'.format(' '.join(args))
         ]