DAPS spellcheck does not check default language

[dariavladykina]

In the DAPS User Guide we state that DAPS "runs a spell check operation on all files in the documentation project with the default dictionary (en_US) with the command daps -d PATH_TO_DC_FILE spellcheck."
However, I get a request to specify the language, so the default en_US is not picked up.
When --lang=en_US is given, it works.

daps -d DC-SLES-tuning spellcheck
Neither file nor rootid specified, using rootid from DC-file
Using language en.
ERROR: Could not automatically determine correct language parameter
(Format must be xx_XX, e.g. en_US), please specify it with --lang