Update "Building a connector the hard way" doc (#9008)

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

@@ -74,7 +74,7 @@ Airbyte provides a code generator which bootstraps the scaffolding for our conne
 
 ```bash
 $ cd airbyte-integrations/connector-templates/generator
-$ ./generate.sh 
+$ ./generate.sh
 ```
 
 We'll select the `generic` template and call the connector `stock-ticker-api`:
@@ -210,7 +210,7 @@ def run(args):
         log("Invalid command. Allowable commands: [spec]")
         sys.exit(1)
 
-    # A zero exit code means the process successfully completed    
+    # A zero exit code means the process successfully completed
     sys.exit(0)
 
 
@@ -287,7 +287,7 @@ Lastly we'll extend the `run` method to accept the `check` command and call the
 def get_input_file_path(path):
     if os.path.isabs(path):
         return path
-    else: 
+    else:
         return os.path.join(os.getcwd(), path)
 ```
 
@@ -559,7 +559,7 @@ def read(config, catalog):
             print(json.dumps(output_message))
 ```
 
-After doing some input validation, the code above calls the API to obtain the last 7 days of prices for the input stock ticker, then outputs the prices in ascending order. As always, our output is formatted according to the Airbyte Specification. Let's update our args parser with the following blocks:
+After doing some input validation, the code above calls the API to obtain the last 7 days of prices for the input stock ticker, then outputs the prices in ascending order (this is only for human-readability; real sources do not need to do this sorting). As always, our output is formatted according to the Airbyte Specification. Let's update our args parser with the following blocks:
 
 ```python
 # Accept the read command
@@ -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:
@@ -1058,8 +1062,8 @@ Armed with the knowledge you gained in this guide, here are some places you can
 This section is not yet complete and will be completed soon. Please reach out to us on [Slack](https://slack.airbyte.io) or [Github](https://github.com/airbytehq/airbyte) if you need the information promised by these sections immediately.
 
 ### Incremental sync
-Follow the [next tutorial](adding-incremental-sync.md) to implement incremental sync. 
+Follow the [next tutorial](adding-incremental-sync.md) to implement incremental sync.
 
 ### Connector Development Kit
-Like we mention at the beginning of the tutorial, this guide is meant more for understanding than as a blueprint for implementing production connectors. See the [Connector Development Kit](../../../airbyte-cdk/python/docs/tutorials/README.md) for the frameworks you should use to build production-ready connectors. 
+Like we mention at the beginning of the tutorial, this guide is meant more for understanding than as a blueprint for implementing production connectors. See the [Connector Development Kit](../../../airbyte-cdk/python/docs/tutorials/README.md) for the frameworks you should use to build production-ready connectors.
 /