CI: Schedule weekly tests with cron

[effigies]

No description provided.

[codecov]

Codecov Report

Merging #3480 (5d5f508) into master (c7972b4) will not change coverage.
The diff coverage is 50.00%.

@@           Coverage Diff           @@
##           master    #3480   +/-   ##
=======================================
  Coverage   65.25%   65.25%           
=======================================
  Files         309      309           
  Lines       40848    40848           
  Branches     5378     5378           
=======================================
  Hits        26657    26657           
  Misses      13117    13117           
  Partials     1074     1074           

Flag	Coverage Δ
unittests	65.03% <50.00%> (ø)

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Impacted Files	Coverage Δ
nipype/pipeline/engine/utils.py	74.97% <50.00%> (ø)

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[effigies]

Tested output in niworkflows. Going to merge and get a hot-fix release out.