narrow: replace "ui.warn(); return 1" by "raise error.Abort()"

This is the usual way of doing it and I don't see a reason to do it
differently here.

Differential Revision: https://phab.mercurial-scm.org/D5468

hgext/narrow/narrowcommands.py

@@ -365,15 +365,13 b' def trackedcmd(ui, repo, remotepath=None'
     """
     opts = pycompat.byteskwargs(opts)
     if repository.NARROW_REQUIREMENT not in repo.requirements:
-        ui.warn(_('The narrow command is only supported on respositories cloned'
-                  ' with --narrow.\n'))
-        return 1
+        raise error.Abort(_('the narrow command is only supported on '
+                            'respositories cloned with --narrow'))
 
     # Before supporting, decide whether it "hg tracked --clear" should mean
     # tracking no paths or all paths.
     if opts['clear']:
-        ui.warn(_('The --clear option is not yet supported.\n'))
-        return 1
+        raise error.Abort(_('the --clear option is not yet supported'))
 
     # import rules from a file
     newrules = opts.get('import_rules')

tests/test-narrow-trackedcmd.t

@@ -196,8 +196,8 b' Testing the --import-rules flag with --a'
   X path:widest
 
   $ hg tracked --import-rules specs --clear
-  The --clear option is not yet supported.
-  [1]
+  abort: the --clear option is not yet supported
+  [255]
 
 Testing with passing a out of wdir file