Make toot instance work with localhost

Asserting the domain exists does not bring much value.

toot/commands.py

@@ -4,7 +4,7 @@ import sys
 
 from toot import api, config
 from toot.auth import login_interactive, login_browser_interactive, create_app_interactive
-from toot.exceptions import ConsoleError, NotFoundError
+from toot.exceptions import ApiError, ConsoleError, NotFoundError
 from toot.output import (print_out, print_instance, print_account, print_acct_list,
                          print_search_results, print_timeline, print_notifications)
 from toot.utils import assert_domain_exists, editor_input, multiline_input, EOF_KEY
@@ -331,12 +331,10 @@ def instance(app, user, args):
     if not name:
         raise ConsoleError("Please specify instance name.")
 
-    assert_domain_exists(name)
-
     try:
         instance = api.get_instance(name, args.scheme)
         print_instance(instance)
-    except NotFoundError:
+    except ApiError:
         raise ConsoleError(
             "Instance not found at {}.\n"
             "The given domain probably does not host a Mastodon instance.".format(name)