fix virtualenv constraint

[dimbleby]

python-poetry/poetry-core#461 reveals that poetry's own pyproject.toml contained an invalid constraint:

Could not parse version constraint: (>=20.4.3

oops.

I still think that poetry-core fix is good and desirable, but if this is an indication of the likely influx of issues... well that's something to think about.

Anyway this MR is clearly good, let's fix the error here.

[dimbleby]

just to confirm:

curl -s https://pypi.org/pypi/poetry/1.2.0/json | jq ".info.requires_dist[3]"
"virtualenv"

ie poetry's metadata is asking for any version of virtualenv at all, not the constrained version that it had thought it was asking for

[poetry-bot]

The backport to 1.2 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.2 1.2
# Navigate to the new working tree
cd .worktrees/backport-1.2
# Create a new branch
git switch --create backport-6376-to-1.2
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 3d0343008ffbd3597509381b4437eeeff12bcf90
# Push it to GitHub
git push --set-upstream origin backport-6376-to-1.2
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.2

Then, create a pull request where the base branch is 1.2 and the compare/head branch is backport-6376-to-1.2.

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.