Fix UnicodeDecodeError in buffer_s3response()

[sir-sigurd]

Description

s3_client.put_object(
    Bucket='quilt-dev-null',
    Key='test-s3-select',
    Body=b''.join(['ы'.encode() * 65 * 2 ** 9, b'\n'] * 2)
)
buffer_s3response(
    s3_client.select_object_content(
        Bucket='quilt-dev-null',
        Key='test-s3-select',
        ExpressionType='SQL',
        Expression='SELECT * FROM s3object s LIMIT 5',
        InputSerialization={'CSV': {}}, OutputSerialization={'CSV': {}}
    )
)
---------------------------------------------------------------------------
UnicodeDecodeError                        Traceback (most recent call last)
<ipython-input-22-f63d210a5ddd> in <module>
     10         ExpressionType='SQL',
     11         Expression='SELECT * FROM s3object s LIMIT 5',
---> 12         InputSerialization={'CSV': {}}, OutputSerialization={'CSV': {}}
     13     )
     14 )

<ipython-input-12-f3176c1b158b> in buffer_s3response(s3response)
     10     for event in s3response['Payload']:
     11         if 'Records' in event:
---> 12             records = event['Records']['Payload'].decode()
     13             response.write(records)
     14             found_records = True

UnicodeDecodeError: 'utf-8' codec can't decode byte 0xd1 in position 64999: unexpected end of data

TODO

• Unit tests
• Changelog entry

[codecov]

Codecov Report

Merging #2123 (706e582) into master (5d49a4c) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 706e582 differs from pull request most recent head 2bd0d66. Consider uploading reports for the commit 2bd0d66 to get more accurate results

@@           Coverage Diff           @@
##           master    #2123   +/-   ##
=======================================
  Coverage   46.35%   46.35%           
=======================================
  Files         429      429           
  Lines       20532    20534    +2     
  Branches     2412     2412           
=======================================
+ Hits         9517     9519    +2     
  Misses      10056    10056           
  Partials      959      959           

Flag	Coverage Δ
api-python	89.71% <ø> (ø)
catalog	16.30% <ø> (ø)
lambda	93.03% <100.00%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
lambdas/shared/t4_lambda_shared/utils.py	98.64% <100.00%> (ø)
lambdas/shared/tests/test_utils.py	97.29% <100.00%> (+0.07%)	⬆️

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