Add a more helpful error message when info() fails with an empty payl…

…oad (#164)

This happens always when the vacuum has not been in contact with
xiaomi's servers and there's nothing else we can do about it

Fixes #156

miio/vacuum_cli.py

@@ -401,10 +401,14 @@ def map(vac: miio.Vacuum):
 @pass_dev
 def info(vac: miio.Vacuum):
     """Return device information."""
-    res = vac.info()
+    try:
+        res = vac.info()
 
-    click.echo("%s" % res)
-    _LOGGER.debug("Full response: %s", pf(res.raw))
+        click.echo("%s" % res)
+        _LOGGER.debug("Full response: %s", pf(res.raw))
+    except TypeError:
+        click.echo("Unable to fetch info, this can happen when the vacuum "
+                   "is not connected to the Xiaomi cloud.")
 
 
 @cli.command()