Add a skip_on_cran()

Author: jennybc

tests/testthat/test-use-course.R

@@ -25,6 +25,8 @@ test_that("conspicuous_place() returns a writeable directory", {
 })
 
 test_that("check_is_zip() errors if MIME type is not 'application/zip'", {
+  ## download timed out on a CRAN submission, so let's not take a chance
+  skip_on_cran()
   ## curl::parse_headers_list() calls trimws()
   ## https://github.com/jeroen/curl/issues/138
   skip_if(getRversion() < 3.2)