Fix pkgresources import iso6

[sanderr]

Description

iso6 sibling of #7866

Self Check:

Strike through any lines that are not applicable (~~line~~) then check the box

• Attached issue to pull request
• Changelog entry
• Type annotations are present
• Code is clear and sufficiently documented
• No (preventable) type errors (check using make mypy or make mypy-diff)
• Sufficient test cases (reproduces the bug/tests the requested feature)
• Correct, in line with design
• End user documentation is included or an issue is created for end-user documentation (add ref to issue here: )
• If this PR fixes a race condition in the test suite, also push the fix to the relevant stable branche(s) (see test-fixes for more info)