feat: use structured logging on GCF with python 3.7 (#434)

Author: daniel-sanche

google/cloud/logging_v2/client.py

@@ -355,13 +355,9 @@ def get_default_handler(self, **kw):
                 return AppEngineHandler(self, **kw)
             elif monitored_resource.type == _GKE_RESOURCE_TYPE:
                 return ContainerEngineHandler(**kw)
-            elif (
-                monitored_resource.type == _GCF_RESOURCE_TYPE
-                and sys.version_info[0] == 3
-                and sys.version_info[1] >= 8
-            ):
-                # Cloud Functions with runtimes > 3.8 supports structured logs on standard out
-                # 3.7 should use the standard CloudLoggingHandler, which sends logs over the network.
+            elif monitored_resource.type == _GCF_RESOURCE_TYPE:
+                # __stdout__ stream required to support structured logging on Python 3.7
+                kw["stream"] = kw.get("stream", sys.__stdout__)
                 return StructuredLogHandler(**kw, project_id=self.project)
             elif monitored_resource.type == _RUN_RESOURCE_TYPE:
                 return StructuredLogHandler(**kw, project_id=self.project)