This was most likely fixed upstream in Stack 1.3.2
https://github.com/commercialhaskell/stack/releases/tag/v1.3.2
With the locale settings from the original bug report and the
command-line below,
the original bug is still trivially reproducible (stretch=1.1.2-7+b1).
However, more recent stack releases (buster=1.7.1-3) just work:
$ stack --resolver lts-12.26 new test yesod-sqlite
Downloading template "yesod-sqlite" to create project "test" in test/
...
Looking for .cabal or package.yaml files to use to init the project.
Using cabal packages:
- test/
Downloaded lts-12.26 build plan.
Selected resolver: lts-12.26
Initialising configuration using resolver: lts-12.26
Total number of user packages considered: 1
Writing configuration to file: test/stack.yaml
All done.
