close #454; some guard on runaway roots

[jverzani]

• Close issue #454
• Some check on runaway zeros due to reltol. Likely needs to be tweaked.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.24%. Comparing base (4263c76) to head (743682d).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #435      +/-   ##
==========================================
+ Coverage   86.21%   86.24%   +0.03%     
==========================================
  Files          38       38              
  Lines        2408     2414       +6     
==========================================
+ Hits         2076     2082       +6     
  Misses        332      332              

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