Handle invalid proportions

[molpopgen]

See #576

[molpopgen]

CI is broken. Gotta fix that first....

[grahamgower]

It looks like the runner is trying to execute:

pip install --upgrade pip pip install -r requirements.txt

Which kinda makes sense in light of the error message:

ERROR: Could not find a version that satisfies the requirement install (from versions: none)
ERROR: No matching distribution found for install

That part of the .yml files hasn't changed, but maybe there's a newline issue here that is newly problematic? Mixed dos/unix newlines?

[molpopgen]

@grahamgower -- I think some of the issue has to do w/the CI being quite out of date. I saw similar errors in the demes-spec PRs before the CI there got updated.

[grahamgower]

The docs build seems to be working here. It's also working for me offline, with Python 3.11. Maybe just rebase this and apply fixes for the proportions? We can do the update to Python 3.12 separately.

[grahamgower]

LGTM.

[grahamgower]

Oooh, codecov isn't broken, it really is just overloaded!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.81%. Comparing base (1c38a2f) to head (b579855).
Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #577   +/-   ##
=======================================
  Coverage   99.81%   99.81%           
=======================================
  Files           5        5           
  Lines        1597     1600    +3     
=======================================
+ Hits         1594     1597    +3     
  Misses          3        3           

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[molpopgen]

@grahamgower -- I made the minimal changes needed for tests to pass. codecov is still failing.