error message fix

slapos/recipe/symbolic_link.py

@@ -51,7 +51,7 @@ class Recipe:
       if os.path.lexists(link):
         if not os.path.islink(link):
           raise zc.buildout.UserError(
-              'Target link already %r exists but it is not link' % link)
+              'Target %r already exists but is not a link' % link)
         os.unlink(link)
       os.symlink(linkline, link)
       self.logger.debug('Created link %r -> %r' % (link, linkline))