Add the enviromental variable to check for URIs.

[llrs]

This should close #401 couldn't test (and saw no formal test for check_for_cran that could modify and adapt).

[codecov-commenter]

Codecov Report

Merging #403 (38b23b7) into master (10449c1) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 38b23b7 differs from pull request most recent head 8a6cb4b. Consider uploading reports for the commit 8a6cb4b to get more accurate results

@@           Coverage Diff           @@
##           master     #403   +/-   ##
=======================================
  Coverage   28.02%   28.02%           
=======================================
  Files          26       26           
  Lines         892      892           
=======================================
  Hits          250      250           
  Misses        642      642           

Impacted Files	Coverage Δ
R/check-cran.R	0.00% <ø> (ø)

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[gaborcsardi]

Thanks! We definitely need to improve this, but hardwiring the values into the package does not seem optimal to me.

[llrs]

Indeed, I tried a couple of weeks ago to update the PR with the values used by CRAN but it is not as simple as just reading a file.