Make payload arg in tuf cli "lazy"

Other than the regular click File, the LazyFile also has the "name"
attribute, when passing stdin via "-".

We print the name on success.

Signed-off-by: Lukas Puehringer <lukas.puehringer@nyu.edu>

Author: lukpueh

warehouse/cli/tuf.py

@@ -24,7 +24,7 @@ def tuf():
 
 
 @tuf.command()
-@click.argument("payload", type=click.File("rb"), required=True)
+@click.argument("payload", type=click.File("rb", lazy=True), required=True)
 @click.option("--api-server", required=True)
 def bootstrap(payload, api_server):
     """Use payload file to bootstrap RSTUF server."""