fix: Fail on start() instead of silent ignore; encode string during error returns

[gauron99]

add try/except wrapper for start() method to error on failed start; encode strings to bytes in exception returns

observed errors:

silent fail on start()

Lifespan failure — hypercorn silently continues with broken state:

INFO:root:Functions middleware invoking user function
[2026-05-06 07:40:51 +0200] [219186] [WARNING] ASGI Framework Lifespan error, continuing without
Lifespan support
WARNING:hypercorn.error:ASGI Framework Lifespan error, continuing without Lifespan support
[2026-05-06 07:40:51 +0200] [219186] [INFO] Running on http://127.0.0.1:8080 (CTRL + C to quit)
INFO:hypercorn.error:Running on http://127.0.0.1:8080 (CTRL + C to quit)

this will appear to run the function just fine (for a second) and then Error: timed out waiting for function to be ready for 1m0s BUT the function is still listening!

on curl you get

[2026-05-06 09:57:21 +0200] [648316] [ERROR] Error in ASGI Framework
Traceback (most recent call last):
  File ".../func_python/http.py", line 134, in __call__
    await self.f.handle(scope, receive, send)
  File ".../function/func.py", line 85, in handle
    "database": self.db.db_path,
                ^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'db_path'

exception error

  During handling of the above exception, another exception occurred:

  Traceback (most recent call last):
    File ".../func_python/http.py", line 136, in __call__
      await send_exception(send, 500, f"Error: {e}")
    File ".../func_python/http.py", line 188, in send_exception
      await send({
          'type': 'http.response.body', 'body': message,
      })
    File ".../hypercorn/protocol/http_stream.py", line 193, in app_send
      Body(stream_id=self.stream_id, data=bytes(message.get("body", b"")))
                                          ~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
  TypeError: string argument without an encoding

[matejvasek]

/approve
/lgtm

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gauron99, matejvasek

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