convert: workaround for cvsps.cache under Windows In non-cygwin environment, cvsps fails to create its cache directory and redirect its output to stderr. Just ignore the error and capture stderr as well.

adding da/foo
adding foo
% manifest
200 Script output follows


drwxr-xr-x da
-rw-r--r-- 4 foo


200 Script output follows


-rw-r--r-- 4 foo