# cabal sandbox init
Writing a default package environment file to <ROOT>/sandbox.dist/cabal.sandbox.config
Creating a new sandbox at <ROOT>/sandbox.dist/sandbox
# cabal sandbox add-source
# cabal sandbox delete-source
Warning: Sources not registered: "q"

cabal: The sources with the above errors were skipped. ("q")
# cabal sandbox add-source
# cabal sandbox delete-source
Success deleting sources: "p" "q"

Note: 'sandbox delete-source' only unregisters the source dependency, but does not remove the package from the sandbox package DB.

Use 'sandbox hc-pkg -- unregister' to do that.