Correct check for role library/ existence

Fixes #8633

lib/ansible/playbook/play.py

@@ -401,7 +401,7 @@ class Play(object):
             library   = utils.path_dwim(self.basedir, os.path.join(role_path, 'library'))
 
             missing = lambda f: not os.path.isfile(f)
-            if missing(task) and missing(handler) and missing(vars_file) and missing(defaults_file) and missing(meta_file) and missing(library):
+            if missing(task) and missing(handler) and missing(vars_file) and missing(defaults_file) and missing(meta_file) and not os.path.isdir(library):
                 raise errors.AnsibleError("found role at %s, but cannot find %s or %s or %s or %s or %s or %s" % (role_path, task, handler, vars_file, defaults_file, meta_file, library))
 
             if isinstance(role, dict):