Sceptre should handle invalid types passed to the parameters dict gracefully

[alex-harvey-z3q]

Subject of the issue

All commands raise exceptions if parameters is a list instead of a dict. This did not occur in v4.4.2 and relates to the cast parameters feature.

Your environment

• version of sceptre (sceptre --version) master
• version of python (python --version) 3.10
• which OS/distro Ubuntu

Steps to reproduce

Tell us how to reproduce this issue. Please provide sceptre project files if possible, you can use https://plnkr.co/edit/ANFHm61Ilt4mQVgF as a base.

Expected behaviour

Should fail cleanly.

Actual behaviour

In v4.4.2 Sceptre would generate invalid parameters and presumably blow up later e.g.

% sceptre dump-config
...
parameters:
- subnet-08b49bb04f76dddf6
- subnet-032c8e50fb828d6f9
- subnet-08e025d377a8a455e

On the current master branch:

Traceback (most recent call last):
  File "/usr/local/bin/sceptre", line 8, in <module>
    sys.exit(cli())
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/click/decorators.py", line 26, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/app/sceptre/sceptre/cli/helpers.py", line 46, in decorated
    return func(*args, **kwargs)
  File "/app/sceptre/sceptre/cli/list.py", line 197, in list_stacks
    plan = SceptrePlan(context)
  File "/app/sceptre/sceptre/plan/plan.py", line 50, in __init__
    all_stacks, command_stacks = self.config_reader.construct_stacks()
  File "/app/sceptre/sceptre/config/reader.py", line 273, in construct_stacks
    stack = self._construct_stack(rel_path, stack_group_config)
  File "/app/sceptre/sceptre/config/reader.py", line 639, in _construct_stack
    stack = Stack(
  File "/app/sceptre/sceptre/stack.py", line 266, in __init__
    self.parameters = self._cast_parameters(parameters or {})
  File "/app/sceptre/sceptre/stack.py", line 308, in _cast_parameters
    casted_parameters = {k: cast_value(v) for k, v in parameters.items()}
AttributeError: 'list' object has no attribute 'items'