Reset sys.excepthook.

[tonyandrewmeyer]

This code currently has no output, but does fail:

example code

import ops

import scenario

class MyCharm(ops.CharmBase):
    def __init__(self, framework):
        super().__init__(framework)
        framework.observe(self.on.config_changed, self._on_config_changed)

    def _on_config_changed(self, event):
        self.unit.get_container("example").replan()

ctx = scenario.Context(
    MyCharm,
    meta={"name": "my-charm", "containers": {"example": {"resource": "ubuntu-22.04"}}},
)
container = scenario.Container("example", can_connect=False)
state = scenario.State(containers=[container])
out = ctx.run("config-changed", state=state)

$ python /tmp/scenario-102.py ; echo $?
1

This PR resets the sys.excepthook change that ops does (to redirect output to Juju's debug-log), so that instead:

(venv) tameyer@tam-canoncial-1:~/code/ops-scenario$ python /tmp/scenario-102.py ; echo $?
Traceback (most recent call last):
[...]
  File "/home/tameyer/code/ops-scenario/scenario/mocking.py", line 711, in _check_connection
    raise pebble.ConnectionError(msg)
ops.pebble.ConnectionError: Cannot connect to Pebble; did you forget to set can_connect=True for container example?

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
[...]
  File "/home/tameyer/code/ops-scenario/scenario/runtime.py", line 442, in exec
    raise UncaughtCharmError(
scenario.runtime.UncaughtCharmError: Uncaught exception (<class 'ops.pebble.ConnectionError'>) in operator/charm code: <ops.pebble.ConnectionError ('Cannot connect to Pebble; did you forget to set can_connect=True for container example?',)>
1

I think this is more what people would expect (if you're running in pytest then you'd get this type of output anyway, but for cases when not doing that).

Fixes #102

[PietroPasotti]

nice! good catch