Odd pip warning in a multi-package-container

[fubar2]

Pip is warning about mismatched scheme.headers in some logs coming from using quay.io/biocontainers/mulled-v2-c0c9dd2959e833cf8c69ae23a9398ddb0db5c98f:5d3a99482f42f5e17ec122729f67bf7be64df9e9-0 (planemo/git/galaxyxml)
Confirmed inside the container with:

root@7bab7f7af205:/# pip install setuptools
WARNING: Value for scheme.headers does not match. Please report this to <https://github.com/pypa/pip/issues/9617>
distutils: /usr/local/include/python3.8/UNKNOWN
sysconfig: /usr/local/include/python3.8
WARNING: Additional context:
user = False
home = None
root = None
prefix = None