Fix Message Consumer Example

[JP-Ellis]

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Prerequisites

• I'm using the latest version of pact-python.
• I have read the console error message carefully (if applicable).

Description

The current master branch has a bug in one of the examples. See for example the result of this job done against ab02630.

Reproducible demo

No response

Steps to reproduce

See master branch

Expected behavior

Test should succeed

Actual behavior

=================================== FAILURES ===================================
_______________________________ test_write_file ________________________________

pact = <pact.message_pact.MessagePact object at 0x7f595b22ba90>
handler = <examples.src.message.Handler object at 0x7f595b2290d0>

    def test_write_file(pact: MessagePact, handler: Handler) -> None:
        """
        Test write file.
    
        This test will be run against the mock provider. The mock provider will
        expect to receive a request to write a file, and will respond with a 200
        status code.
        """
        msg = {"action": "WRITE", "path": "test.txt", "contents": "Hello world!"}
        (
            pact.given("a request to write test.txt")
            .expects_to_receive("empty filesystem")
            .with_content(msg)
            .with_metadata({"Content-Type": "application/json"})
        )
    
>       result = handler.process(msg)

examples/tests/test_02_message_consumer.py:119: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <examples.src.message.Handler object at 0x7f[59](https://github.com/pact-foundation/pact-python/actions/runs/6619870924/job/17981208903#step:7:60)5b2290d0>
event = {'action': 'WRITE', 'contents': 'Hello world!', 'path': 'test.txt'}

    def process(self, event: Dict[str, Any]) -> Union[str, None]:
        """
        Process an event from the queue.
    
        The event is expected to be a dictionary with the following mandatory
        keys:
    
        - `action`: The action to be performed, either `READ` or `WRITE`.
        - `path`: The path to the file to be read or written.
    
        The event may also contain an optional `contents` key, which is the
        contents to be written to the file. If the `contents` key is not
        present, an empty file will be written.
        """
        self.validate_event(event)
    
        if event["action"] == "WRITE":
            self.fs.write(event["path"], event.get("contents", ""))
        if event["action"] == "READ":
            return self.fs.read(event["path"])
    
        msg = "Invalid action."
>       raise ValueError(msg)
E       ValueError: Invalid action.

examples/src/message.py:[68](https://github.com/pact-foundation/pact-python/actions/runs/6619870924/job/17981208903#step:7:69): ValueError

Your environment

Pact Python CI

Self-service

• I'd be willing to fix this bug myself.