diff can now be a list

lib/ansible/plugins/callback/__init__.py

@@ -72,7 +72,13 @@ class CallbackBase:
             for warning in res['warnings']:
                 self._display.warning(warning)
 
-    def _get_diff(self, diff):
+    def _get_diff(self, difflist):
+
+        if not isinstance(difflist, list):
+            difflist = [difflist]
+
+        ret = []
+        for diff in difflist:
             try:
                 with warnings.catch_warnings():
                     warnings.simplefilter('ignore')
@@ -95,11 +101,11 @@ class CallbackBase:
                         else:
                             after_header = 'after'
                         differ = difflib.unified_diff(to_unicode(diff['before']).splitlines(True), to_unicode(diff['after']).splitlines(True), before_header, after_header, '', '', 10)
-                    for line in list(differ):
-                        ret.append(line)
+                        ret.extend(list(differ))
+                        ret.append('\n')
                     return u"".join(ret)
             except UnicodeDecodeError:
-            return ">> the files are different, but the diff library cannot compare unicode strings"
+                ret.append(">> the files are different, but the diff library cannot compare unicode strings\n\n")
 
     def _process_items(self, result):