Ease cutoff between poly and frd method for stability margins#575

Merged

murrayrm merged 2 commits intopython-control:masterfrom

bnavigator:add-frd-margin-test

Mar 19, 2021

Commits on Mar 17, 2021

merge the second example from #523 into test_stability_margins_discrete
bnavigator
committed
improve error message display, ease poly to frd check
bnavigator
committed