Improve error handling of `datalad-annex::` git remote helper about datalad-next HOT 2 CLOSED

❯ datalad clone 'datalad-annex::file:///tmp/invalidpath?type=directory&encryption=none&directory={path}' t1
install(error): /tmp/t1 (dataset) [Failed to clone from any candidate source URL. Encountered errors per each url were:
- datalad-annex::file:///tmp/invalidpath?type=directory&encryption=none&directory={path}
  CommandError: 'git -c diff.ignoreSubmodules=none -c core.quotepath=false clone --progress 'datalad-annex::file:///tmp/invalidpath?type=directory&encryption=none&directory={path}' /tmp/t1' failed with exitcode 128 [err: 'Cloning into '/tmp/t1'...
fatal: CommandError(CommandError: 'git -c diff.ignoreSubmodules=none -c core.quotepath=false annex initremote origin type=directory encryption=none directory=/tmp/invalidpath -c annex.dotfiles=true' failed with exitcode 1 under /tmp/t1/.git/dl-repoannex/origin/repoannex [out: 'initremote origin 
failed'] [err: 'git-annex: Directory does not exist: /tmp/invalidpath
initremote: 1 failed'])
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.']]

❯ datalad clone 'datalad-annex::file:///tmp/validpath?type=directory&encryption=none&directory={path}' t1
[WARNING] You appear to have cloned an empty repository.                                     
[WARNING] Cloned /tmp/t1 but could not find a branch with commits                            
install(ok): /tmp/t1 (dataset)