add airbyte_entrypoint env var

docs/connector-development/tutorials/build-a-connector-the-hard-way.md

@@ -836,7 +836,7 @@ A full connector in less than 200 lines of code. Not bad! We're now ready to pac
 
 Our connector is very lightweight, so the Dockerfile needed to run it is very light as well. We edit the autogenerated `Dockerfile` so that its contents are as followed:
 
-```text
+```Dockerfile
 FROM python:3.7-slim
 
 # We change to a directory unique to us
@@ -853,6 +853,10 @@ ENTRYPOINT ["python", "/airbyte/integration_code/source.py"]
 # Airbyte's build system uses these labels to know what to name and tag the docker images produced by this Dockerfile.
 LABEL io.airbyte.name=airbyte/source-stock-ticker-api
 LABEL io.airbyte.version=0.1.0
+
+# In order to launch a source on Kubernetes in a pod, we need to be able to wrap the entrypoint.
+# The source connector must specify its entrypoint in the AIRBYTE_ENTRYPOINT variable.
+ENV AIRBYTE_ENTRYPOINT='python /airbyte/integration_code/source.py'
 ```
 
 Once we save the `Dockerfile`, we can build the image by running: