Add explicit text mode to zopen calls (monty warning)

[rkingsbury]

Add explicit test mode to zopen calls to resolve monty warning.

Fixes #1024

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.91%. Comparing base (9bc96da) to head (9da353e).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1025   +/-   ##
=======================================
  Coverage   88.91%   88.91%           
=======================================
  Files          46       46           
  Lines        3997     3997           
=======================================
  Hits         3554     3554           
  Misses        443      443           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.