Update autocompose.py

Print error message to stderr so that I will be seen when redirecting stdout to `docker-compose.yml`

Author: moschlar

autocompose.py

@@ -32,7 +32,7 @@ def generate(cname):
     try:
         cid = [x.short_id for x in c.containers.list(all=True) if cname == x.name or x.short_id in cname][0]
     except IndexError:
-        print("That container is not available.")
+        print("That container is not available.", file=sys.stderr)
         sys.exit(1)
 
     cattrs = c.containers.get(cid).attrs