After a recent software package update of my VPS, aws-cli version 1.37 was installed.
This version broke my regular backup to s3 task since aws s3 cp ... abended now with the following error

TypeError: argument of type 'NoneType' is not iterable

I searched the net and found some appropriate bug reports:
SignatureDoesNotMatch when putting file #9236
Content-MD5 header is not set anymore for PutBucketLifecycleConfiguration operation #3415

Both issues were already closed and announced to be fixed in an upcoming version.

But upgrading to the next version didn't solve my problem.
So I decided to revert back to a recent working version, which turned out to be not as easy on Archlinux.

1. First I deinstalled every target and conflicting package version to avoid later file conflicts.
   

   sudo yay -R aws-cli python-botocore python-rsa python-docutils

2. Then i installed missing python build requirements
   

   sudo yay -S git python-pip python-virtualenv

3. Checking out the source code
   

   cd /usr/src/build/
   git clone https://github.com/aws/aws-cli.git
   cd aws-cli/
   git checkout 1.36.34

4. Building the former version of aws-cli in a venv
   

   virtualenv venv
   . venv/bin/activate
   pip install --upgrade pip
   pip install -r requirements.txt
   pip install -e .

5. Installing aws-cli and dependent packages system-wide using pip
   

   deactivate
   sudo pip install --break-system-packages [--dry-run] .

I hope this short guide helps some people having the same issue.

🔥 But keep in mind, that installing python packages system-wide via pip is strongly discouraged as it may break your system.
🥳 However I didn't experience any such problems.