[EM] proportional constraints - help needed

[Raph Frank]

What about this rule, if simplicity is required.

1) Run a standard PR-STV election.
2) If the result violates the criterion
- permanently eliminate the weakest candidate of the over-represented
gender and repeat

The first candidate to be eliminated is weakest and the first
candidate to be elected is strongest.  If two candidates are elected
in the same round, they can be ordered based on total votes held when
elected.

This has the advantage of being simple and might even complete with a
single pass and hopefully not to many passes.

You can eliminate multiple candidates in a single pass if they were
all eliminated one after another.  This is the standard PR-STV
multiple elimination rule.

So, if the election goes:

A) <Round(s) of candidates exceeding the quota>
B) <Round(s) of candidates being eliminated>
C) <Round(s)

Then all candidates eliminated in step B, can be eliminated as a bloc.