update unit test err msg, closes #4769

[jangorecki]

closes #4769
passed on 2020-10-20 r79356 https://gitlab.com/jangorecki/data.table/-/jobs/803180097
R change 2020-10-20 r79353

[codecov]

Codecov Report

Merging #4770 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4770   +/-   ##
=======================================
  Coverage   99.47%   99.47%           
=======================================
  Files          73       73           
  Lines       14556    14556           
=======================================
  Hits        14480    14480           
  Misses         76       76           

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[mattdowle]

I changed the pattern to be minimal in case of any similar minor changes to R's message in future. We should probably review all tests that look for R's messages, and similarly relax them. Not sure how to find them though.

For the news item, I took it as an opportunity to give credit to CRAN.

[MichaelChirico]

Not sure how to find them though.

suggestion -- run an R session in chinese & run tests. i think you'll need to tweak test.data.table() since we made that change for non-english sessions