ImportError: cannot import name 'string_types' from 'six' while testing with uv --resolution=lowest

[pcjedi]

Describe the bug

Package maintainers who use uv to test the lowest possible set of dependencies for their Python packages and have boto3/botocore as dependencies will encounter this issue.

uv resolves the lowest version of dependencies, and in this case, it installs:

• python-dateutil==2.1 (minimum version allowed by botocore).
• six==0.9.0 (the lowest available version since python-dateutil==2.1 does not constrain six).

This combination is incompatible and results in the following error during imports:

ImportError: cannot import name 'string_types' from 'six'

This specifically impacts the maintainers testing their packages with uv --resolution=lowest

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

Package maintainers testing with uv pip install --resolution=lowest should not encounter incompatible dependency installations when relying on the latest version of boto3/botocore. The dependency resolution process should prevent incompatible versions of python-dateutil and six from being installed.

Current Behavior

When resolving dependencies with uv --resolution=lowest, boto3 and botocore allow the installation of the following versions:

boto3==1.36.0
botocore==1.36.0
python-dateutil==2.1
six==0.9.0

This combination is incompatible, resulting in the error:

ImportError: cannot import name 'string_types' from 'six'

Reproduction Steps

1. Install the following versions manually:

pip install "boto3==1.36.0" "six<1"

2. Attempt to import boto3:

python -c "import boto3"

or

1. Create a Python package that depends on boto3/botocore
2. Test the package with uv --resolution=lowest

Example:
https://github.com/pcjedi/botocoredep/actions/runs/12786849699/job/35644776921

Possible Solution

Update the python-dateutil version constraint in botocore to >=2.4, which ensures compatibility with six.

Note: During testing, it was found that all tests in botocore passed successfully only with python-dateutil>=2.7. To ensure broader compatibility, consider raising the constraint to python-dateutil>=2.7.

Additional Information/Context

This issue specifically affects package maintainers relying on boto3/botocore and testing with uv --resolution=lowest

SDK version used

1.36.0

Environment details (OS name and version, etc.)

debian