`wkg get -o some_dir/` gives confusing error if `some_dir` doesn't exist

[itowlson]

$ wkg get fermyon:spin@3.0.0 -o WIT-TEST2/ --format wit --registry registrytest-vfztdiyy.fermyon.app
Getting fermyon:spin@3.0.0...
Error: No such file or directory (os error 2) at path "/home/ivan/testing/s3regtest/WIT-TEST2/.wkg-getT7LRZK"

The actual problem is that WIT-TEST2 doesn't exist (and wkg is reluctant to create it), but the temporary file name sends me in the wrong direction. It would be more helpful if wkg either:

• created the directory; or
• printed e.g. "directory WIT-TEST2 does not exist"