Fix parse yaml error with python3.8

[Carlangueitor]

Proposed changes

In python 3.8 changing the keys of a dict during iteration of the dict itself can raise RuntimeErrors, specifically I got this error in plan while triying to add a Helm Chart:

  pulumi:pulumi:Stack (monitoring-staging):                                                                                                                                                                      
    error: Program failed with an unhandled exception:                                                                                                                                                           
    error: Traceback (most recent call last):                                                                                                                                                                    
      File "/home/charly/.pulumi/bin/pulumi-language-python-exec", line 85, in <module>                                                                                                                          
        loop.run_until_complete(coro)                                                                                                                                                                            
      File "/usr/lib/python3.8/asyncio/base_events.py", line 612, in run_until_complete                                                                                            
        return future.result()                                                                                                                                                     
      File "/usr/lib/python3.8/site-packages/pulumi/output.py", line 155, in run                                                                                                   
        value = await self._future                                                                                                                                                 
      File "/usr/lib/python3.8/site-packages/pulumi/runtime/stack.py", line 81, in run_in_stack                                                                                    
        await run_pulumi_func(lambda: Stack(func))                                                                                                                                 
      File "/usr/lib/python3.8/site-packages/pulumi/runtime/stack.py", line 50, in run_pulumi_func                                                                                 
        await RPC_MANAGER.rpcs.pop()                                                                                                                                               
      File "/usr/lib/python3.8/site-packages/pulumi/runtime/rpc_manager.py", line 67, in rpc_wrapper                                                                               
        result = await rpc                                                                                                                                                         
      File "/usr/lib/python3.8/site-packages/pulumi/runtime/resource.py", line 440, in do_register_resource_outputs                                                                
        serialized_props = await rpc.serialize_properties(outputs, {})                                                                                                             
      File "/usr/lib/python3.8/site-packages/pulumi/runtime/rpc.py", line 68, in serialize_properties                                                                              
        result = await serialize_property(v, deps, input_transformer)                                                                                                              
      File "/usr/lib/python3.8/site-packages/pulumi/runtime/rpc.py", line 173, in serialize_property                                                                               
        value = await serialize_property(output.future(), deps, input_transformer)                                                                                                 
      File "/usr/lib/python3.8/site-packages/pulumi/runtime/rpc.py", line 159, in serialize_property                                                                               
        future_return = await asyncio.ensure_future(awaitable)                                                                                                                     
      File "/usr/lib/python3.8/site-packages/pulumi/output.py", line 340, in gather_futures                                                                                        
        return await asyncio.gather(*value_futures)                                                                                                                                
      File "/usr/lib/python3.8/site-packages/pulumi/output.py", line 114, in get_value                                                                                             
        val = await self._future                                                                                                                                                   
      File "/usr/lib/python3.8/site-packages/pulumi/output.py", line 186, in run                                                                                                   
        return await transformed.future(with_unknowns=True)                                                                                                                        
      File "/usr/lib/python3.8/site-packages/pulumi/output.py", line 114, in get_value                                                                                             
        val = await self._future                                                                                                                                                   
      File "/usr/lib/python3.8/site-packages/pulumi/output.py", line 114, in get_value                                                                                             
        val = await self._future                                                                                                                                                   
      File "/usr/lib/python3.8/site-packages/pulumi/output.py", line 155, in run                                                                                                   
        value = await self._future                                                                                                                                                 
      File "/usr/lib/python3.8/site-packages/pulumi/output.py", line 176, in run                                                                                                   
        transformed: Input[U] = func(value)                                                                                                                                        
      File "/usr/lib/python3.8/site-packages/pulumi_kubernetes/helm/v2/helm.py", line 362, in <lambda>                                                                             
        lambda objects: _parse_yaml_document(objects, opts, config.transformations))                                                                                               
      File "/usr/lib/python3.8/site-packages/pulumi_kubernetes/yaml.py", line 122, in _parse_yaml_document                                                                         
        file_objects = _parse_yaml_object(obj, opts, transformations, resource_prefix)                                                                                             
      File "/usr/lib/python3.8/site-packages/pulumi_kubernetes/yaml.py", line 177, in _parse_yaml_object
        for key in obj:
    RuntimeError: dictionary keys changed during iteration

A fix for this is iterate over a copy of the keys instead of iterate the dict itself.

Related issues (optional)

[lblackstone]

LGTM - thanks for the fix!