Add test for https://github.com/ansible/ansible/issues/9851

test/integration/roles/test_filters/files/9851.txt

@@ -0,0 +1,3 @@
+ [{
+    "k": "Quotes \"'\n"
+}]

test/integration/roles/test_filters/tasks/main.yml

@@ -25,6 +25,25 @@
 - name: Verify that we workaround a py26 json bug
   template: src=py26json.j2 dest={{output_dir}}/py26json.templated mode=0644
 
+- name: 9851 - Verify that we don't trigger https://github.com/ansible/ansible/issues/9851
+  copy:
+    content: " [{{item|to_nice_json}}]"
+    dest: "{{output_dir}}/9851.out"
+  with_items:
+  - {"k": "Quotes \"'\n"}
+
+- name: 9851 - copy known good output into place
+  copy: src=9851.txt dest={{output_dir}}/9851.txt
+
+- name: 9851 - Compare generated json to known good
+  shell: diff {{output_dir}}/9851.out {{output_dir}}/9851.txt
+  register: 9851_diff_result
+
+- name: 9851 - verify generated file matches known good
+  assert:  
+    that: 
+        - '9851_diff_result.stdout == ""' 
+
 - name: fill in a basic template
   template: src=foo.j2 dest={{output_dir}}/foo.templated mode=0644
   register: template_result