Random SignatureDoesNotMatch

I am syncing from gcloud to AWS and I am randomly getting these exceptions:

```
cache-control:must-revalidate, max-age=0
content-disposition:inline
content-length:6046
content-md5:vKgMKPFCMKFguMtm9roGBw==
content-type:image/jpeg
expect:100-Continue
host:goout-assets-backups.s3.eu-central-1.amazonaws.com
user-agent:Boto/2.49.0 Python/3.7.3 Linux/5.4.120+ gsutil/4.68 (linux) analytics/disabled interactive/False command/rsync-DaisyChain google-cloud-sdk/358.0.0
x-amz-content-sha256:fc0eda0d7a1f68caf6b317935cc3a281249b3e36469a9b3995639494c0abf28e
x-amz-date:20210925T204805Z
x-amz-meta-surrogate-control:max-age=31536000,max-age=31536000
x-goog-hash:md5=vKgMKPFCMKFguMtm9roGBw==

cache-control;content-disposition;content-length;content-md5;content-type;expect;host;user-agent;x-amz-content-sha256;x-amz-date;x-amz-meta-surrogate-control;x-goog-hash
fc0eda0d7a1f68caf6b317935cc3a281249b3e36469a9b3995639494c0abf28e50 55 54 0a 2f 69 2f 75 73 65 72 2f 31 33 38 36 35 32 39 5f 30 30 31 5f 6d 69 6e 2e 6a 70 67 0a 0a 63 61 63 68 65 2d 63 6f 6e 74 72 6f 6c 3a 6d 75 73 74 2d 72 65 76 61 6c 69 64 61 74 65 2c 20 6d 61 78 2d 61 67 65 3d 30 0a 63 6f 6e 74 65 6e 74 2d 64 69 73 70 6f 73 69 74 69 6f 6e 3a 69 6e 6c 69 6e 65 0a 63 6f 6e 74 65 6e 74 2d 6c 65 6e 67 74 68 3a 36 30 34 36 0a 63 6f 6e 74 65 6e 74 2d 6d 64 35 3a 76 4b 67 4d 4b 50 46 43 4d 4b 46 67 75 4d 74 6d 39 72 6f 47 42 77 3d 3d 0a 63 6f 6e 74 65 6e 74 2d 74 79 70 65 3a 69 6d 61 67 65 2f 6a 70 65 67 0a 65 78 70 65 63 74 3a 31 30 30 2d 43 6f 6e 74 69 6e 75 65 0a 68 6f 73 74 3a 67 6f 6f 75 74 2d 61 73 73 65 74 73 2d 62 61 63 6b 75 70 73 2e 73 33 2e 65 75 2d 63 65 6e 74 72 61 6c 2d 31 2e 61 6d 61 7a 6f 6e 61 77 73 2e 63 6f 6d 0a 75 73 65 72 2d 61 67 65 6e 74 3a 42 6f 74 6f 2f 32 2e 34 39 2e 30 20 50 79 74 68 6f 6e 2f 33 2e 37 2e 33 20 4c 69 6e 75 78 2f 35 2e 34 2e 31 32 30 2b 20 67 73 75 74 69 6c 2f 34 2e 36 38 20 28 6c 69 6e 75 78 29 20 61 6e 61 6c 79 74 69 63 73 2f 64 69 73 61 62 6c 65 64 20 69 6e 74 65 72 61 63 74 69 76 65 2f 46 61 6c 73 65 20 63 6f 6d 6d 61 6e 64 2f 72 73 79 6e 63 2d 44 61 69 73 79 43 68 61 69 6e 20 67 6f 6f 67 6c 65 2d 63 6c 6f 75 64 2d 73 64 6b 2f 33 35 38 2e 30 2e 30 0a 78 2d 61 6d 7a 2d 63 6f 6e 74 65 6e 74 2d 73 68 61 32 35 36 3a 66 63 30 65 64 61 30 64 37 61 31 66 36 38 63 61 66 36 62 33 31 37 39 33 35 63 63 33 61 32 38 31 32 34 39 62 33 65 33 36 34 36 39 61 39 62 33 39 39 35 36 33 39 34 39 34 63 30 61 62 66 32 38 65 0a 78 2d 61 6d 7a 2d 64 61 74 65 3a 32 30 32 31 30 39 32 35 54 32 30 34 38 30 35 5a 0a 78 2d 61 6d 7a 2d 6d 65 74 61 2d 73 75 72 72 6f 67 61 74 65 2d 63 6f 6e 74 72 6f 6c 3a 6d 61 78 2d 61 67 65 3d 33 31 35 33 36 30 30 30 2c 6d 61 78 2d 61 67 65 3d 33 31 35 33 36 30 30 30 0a 78 2d 67 6f 6f 67 2d 68 61 73 68 3a 6d 64 35 3d 76 4b 67 4d 4b 50 46 43 4d 4b 46 67 75 4d 74 6d 39 72 6f 47 42 77 3d 3d 0a 0a 63 61 63 68 65 2d 63 6f 6e 74 72 6f 6c 3b 63 6f 6e 74 65 6e 74 2d 64 69 73 70 6f 73 69 74 69 6f 6e 3b 63 6f 6e 74 65 6e 74 2d 6c 65 6e 67 74 68 3b 63 6f 6e 74 65 6e 74 2d 6d 64 35 3b 63 6f 6e 74 65 6e 74 2d 74 79 70 65 3b 65 78 70 65 63 74 3b 68 6f 73 74 3b 75 73 65 72 2d 61 67 65 6e 74 3b 78 2d 61 6d 7a 2d 63 6f 6e 74 65 6e 74 2d 73 68 61 32 35 36 3b 78 2d 61 6d 7a 2d 64 61 74 65 3b 78 2d 61 6d 7a 2d 6d 65 74 61 2d 73 75 72 72 6f 67 61 74 65 2d 63 6f 6e 74 72 6f 6c 3b 78 2d 67 6f 6f 67 2d 68 61 73 68 0a 66 63 30 65 64 61 30 64 37 61 31 66 36 38 63 61 66 36 62 33 31 37 39 33 35 63 63 33 61 32 38 31 32 34 39 62 33 65 33 36 34 36 39 61 39 62 33 39 39 35 36 33 39 34 39 34 63 30 61 62 66 32 38 65SMF0E246JA6D3MFJhdCE4iVd4ajCS63qGjwga2K+9RoGbxoGMwOqgCnoLWpk8IpQSTIplRUJdcnMInfjdynMmZdMwqw=
Copying gs://store-production/i/user/1386583_001_app.jpg [Content-Type=image/jpeg]...
AccessDeniedException: 403 SignatureDoesNotMatch

SignatureDoesNotMatchThe request signature we calculated does not match the signature you provided. Check your key and signing method.AKIA2ANDJRW3KYFISZTBAWS4-HMAC-SHA256
20210925T204805Z
20210925/eu-central-1/s3/aws4_request
f90ac4e627483fa8457bd23bc5c38f66ffdd47ddb1f090d991fb240970c4f93f6c78a8d879a99e7f23b6113d2b6854953080d792f729a13313323006456a29dc41 57 53 34 2d 48 4d 41 43 2d 53 48 41 32 35 36 0a 32 30 32 31 30 39 32 35 54 32 30 34 38 30 35 5a 0a 32 30 32 31 30 39 32 35 2f 65 75 2d 63 65 6e 74 72 61 6c 2d 31 2f 73 33 2f 61 77 73 34 5f 72 65 71 75 65 73 74 0a 66 39 30 61 63 34 65 36 32 37 34 38 33 66 61 38 34 35 37 62 64 32 33 62 63 35 63 33 38 66 36 36 66 66 64 64 34 37 64 64 62 31 66 30 39 30 64 39 39 31 66 62 32 34 30 39 37 30 63 34 66 39 33 66PUT
/i/user/1386570_001_app.jpg
```

version:

```
user-agent:Boto/2.49.0 Python/3.7.3 Linux/5.4.120+ gsutil/4.68
```

No source file or test is named. Start by reproducing the gcloud-to-AWS S3 rsync with the reported gsutil, Boto, Python, and Linux versions, then compare successful and failing canonical requests; done means the intermittent SignatureDoesNotMatch failure is explained and no longer occurs in the tested sync.

Written by the indexing model from the issue text.