prefect: Inconsistent configuration of S3Result vs S3 Storage with custom S3 backend

Description

The following S3 storage configuration works as expected when connecting to Minio:

storage = S3(
        bucket="flows",
        aws_access_key_id=os.getenv("MY_MINIO_ID"),
        aws_secret_access_key=os.getenv("MY_MINIO_KEY"),
        client_options=dict(endpoint_url=os.getenv("MINIO_ENDPOINT")),
    )

Although when trying to work with S3Result:

    result = S3Result(
        bucket="results",
        boto3_kwargs=dict(
            aws_access_key_id=os.getenv("MY_MINIO_ID"),
            aws_secret_access_key=os.getenv("MY_MINIO_KEY"),
            client_options=dict(endpoint_url=os.getenv("MINIO_ENDPOINT")),
        ),
    )

I receive the following error in UI:

prefect-agent_1      | [2020-06-09 07:59:36] DEBUG - prefect.S3Result | Starting to upload result to 2020/6/9/5a96e8ef-70d1-4d47-a495-15b0afa99169.prefect_result...
prefect-agent_1      | [2020-06-09 07:59:36] ERROR - prefect.CloudTaskRunner | Unexpected error: TypeError("client() got multiple values for keyword argument 'aws_access_key_id'")
prefect-agent_1      | Traceback (most recent call last):
prefect-agent_1      |   File "/usr/local/lib/python3.7/site-packages/prefect/engine/runner.py", line 48, in inner
prefect-agent_1      |     new_state = method(self, state, *args, **kwargs)
prefect-agent_1      |   File "/usr/local/lib/python3.7/site-packages/prefect/engine/task_runner.py", line 986, in get_task_run_state
prefect-agent_1      |     result = self.result.write(value, filename="output", **prefect.context)
prefect-agent_1      |   File "/usr/local/lib/python3.7/site-packages/prefect/engine/results/s3_result.py", line 103, in write
prefect-agent_1      |     self.client.upload_fileobj(stream, Bucket=self.bucket, Key=new.location)
prefect-agent_1      |   File "/usr/local/lib/python3.7/site-packages/prefect/engine/results/s3_result.py", line 60, in client
prefect-agent_1      |     self.initialize_client()
prefect-agent_1      |   File "/usr/local/lib/python3.7/site-packages/prefect/engine/results/s3_result.py", line 49, in initialize_client
prefect-agent_1      |     "s3", credentials=None, use_session=True, **self.boto3_kwargs
prefect-agent_1      |   File "/usr/local/lib/python3.7/site-packages/prefect/utilities/aws.py", line 49, in get_boto_client
prefect-agent_1      |     **kwargs
prefect-agent_1      | TypeError: client() got multiple values for keyword argument 'aws_access_key_id'

Expected Behavior

Expectation is to be able to configure S3Result by directly passing boto3 arguments (same as it works for S3 storage) and have consistency across these 2 structures.

Reproduction

Sample flow I’m using:

import os
from prefect import task, Flow
from prefect.engine.results.s3_result import S3Result
from prefect.environments.storage import Docker

@task
def add(x, y=1):
    """
    The only task we use so far here ;-)
    """
    return x + y

def create_flow():
    """
    Create the flow
    """
    result = S3Result(
        bucket="results",
        boto3_kwargs=dict(
            aws_access_key_id=os.getenv("MY_MINIO_ID"),
            aws_secret_access_key=os.getenv("MY_MINIO_KEY"),
            client_options=dict(endpoint_url=os.getenv("MINIO_ENDPOINT")),
        ),
    )

    with Flow("Sample Flow", result=result) as flow:
        first_result = add(1, y=2)
        second_result = add(x=first_result, y=100)
    
    storage = Docker()
    storage.add_flow(flow)
    flow.storage = storage

    return flow

Environment

Any additional information about your environment

• OSX
• Docker Compose
• Docker Agent

Optionally run prefect diagnostics from the command line and paste the information here

root@9675cb8de5d4:/opt/packages# prefect diagnostics
{
  "config_overrides": {},
  "env_vars": [
    "PREFECT__LOGGING__LEVEL",
    "PREFECT__SERVER__HOST",
    "PREFECT__BACKEND"
  ],
  "system_information": {
    "platform": "Linux-4.19.76-linuxkit-x86_64-with-debian-10.4",
    "prefect_version": "0.11.5",
    "python_version": "3.7.7"
  }
}