Yamale command line treats pipes as directories

[ajuniper]

If I use a shell process substitution like this:

yamale schema.yaml <( process_which_outputs_yaml_to_validate )

or

command pipeline | yamale schema.yaml /dev/stdin

then validation fails because yamale receives the PATH argument as e.g. /dev/fd/63 which fails the os.path.isfile test at command_line.py line 103, and is therefore treated as a directory.

Switching line 103 to be if not os.path.isdir(root): means it behaves correctly.