Make assertion less specific so it doesn't assert on implementation details and

works with older and newer versions of mongoengine.

Author: Kami

robotfm_tests/docs/quickstart_sample_rule_with_webhook.rst

@@ -35,7 +35,8 @@
         ${result}=       Run Process    st2  rule  create  /usr/share/doc/st2/examples/rules/sample_rule_with_webhook.yaml  -j
         Should Contain   ${result.stdout}  ERROR: 409 Client Error: Conflict
         Should Contain   ${result.stdout}  MESSAGE: Tried to save duplicate unique keys
-        Should Contain   ${result.stdout}  duplicate key error collection: st2.rule_d_b index: uid_1 dup key: { : "rule:examples:sample_rule_with_webhook" }) for url:
+        Should Contain   ${result.stdout}  duplicate key error
+        Should Contain   ${result.stdout}  { : "rule:examples:sample_rule_with_webhook" }
 
     Verify rule status
         ${TOKEN}=        Run Process    st2  auth  -p  Ch@ngeMe  st2admin  -t  shell=True