Tests `list_comments_not_found_by_account/list_comments_not_found_by_permlink` work

hivemind/tavern/database_api_patterns/list_comments_not_found_by_account.pat.json

 {
-  "code": -32003,
-  "data": {
-    "code": 10,
-    "message": "Assert Exception",
-    "name": "assert_exception",
-    "stack": [
-      {
-        "context": {
-          "file": "database_api.cpp",
-          "hostname": "",
-          "level": "error",
-          "line": 1015,
-          "method": "list_comments"
-        },
-        "data": {
-          "a": "etcmike",
-          "p": ""
-        },
-        "format": "comment != nullptr: Could not find comment ${a}/${p}."
-      }
-    ]
-  },
-  "message": "Assert Exception:comment != nullptr: Could not find comment etcmike/."
+  "code": -32602,
+  "data": "Post etcmike/ does not exist",
+  "message": "Invalid parameters"
 }

hivemind/tavern/database_api_patterns/list_comments_not_found_by_permlink.pat.json

 {
-  "code": -32003,
-  "data": {
-    "code": 10,
-    "message": "Assert Exception",
-    "name": "assert_exception",
-    "stack": [
-      {
-        "context": {
-          "file": "database_api.cpp",
-          "hostname": "",
-          "level": "error",
-          "line": 1015,
-          "method": "list_comments"
-        },
-        "data": {
-          "a": "",
-          "p": "re-bullionstackers-screen-it-tab-it-what-are-they-20160829t061254603z"
-        },
-        "format": "comment != nullptr: Could not find comment ${a}/${p}."
-      }
-    ]
-  },
-  "message": "Assert Exception:comment != nullptr: Could not find comment /re-bullionstackers-screen-it-tab-it-what-are-they-20160829t061254603z."
+  "code": -32602,
+  "data": "Post /re-bullionstackers-screen-it-tab-it-what-are-they-20160829t061254603z does not exist",
+  "message": "Invalid parameters"
 }

hivemind/tavern/test_database_api_patterns.tavern.yaml

@@ -4,8 +4,6 @@ test_name: Hivemind database_api.list_comments patterns test order "by_cashout_t
 
 marks:
   - patterntest
-  - failing
-  - xfail # should show error when there is only one of optional value (first)
 
 includes:
   - !include common.yaml
@@ -41,8 +39,6 @@ test_name: Hivemind database_api.list_comments patterns test order "by_cashout_t
 
 marks:
   - patterntest
-  - failing
-  - xfail # should show error when there is only one of optional value (second)
 
 includes:
   - !include common.yaml