Adding error handlers to managed vms hello world samples. (#369)

appengine/flexible/hello_world/main.py

@@ -13,6 +13,8 @@
 # limitations under the License.
 
 # [START app]
+import logging
+
 from flask import Flask
 
 
@@ -25,6 +27,14 @@ def hello():
     return 'Hello World!'
 
 
+@app.errorhandler(500)
+def server_error(e):
+    logging.exception('An error occurred during a request.')
+    return """
+    An internal error occurred: <pre>{}</pre>
+    See logs for full stacktrace.
+    """.format(e), 500
+
 if __name__ == '__main__':
     # This is used when running locally. Gunicorn is used to run the
     # application on Google App Engine. See entrypoint in app.yaml.

appengine/flexible/hello_world_compat/main.py

@@ -13,6 +13,8 @@
 # limitations under the License.
 
 # [START app]
+import logging
+
 from flask import Flask
 
 
@@ -23,4 +25,13 @@
 def hello():
     """Return a friendly HTTP greeting."""
     return 'Hello World!'
+
+
+@app.errorhandler(500)
+def server_error(e):
+    logging.exception('An error occurred during a request.')
+    return """
+    An internal error occurred: <pre>{}</pre>
+    See logs for full stacktrace.
+    """.format(e), 500
 # [END app]