fail_with is not allowed in check method. Use vprint_error and return a CheckCode instead.

modules/exploits/multi/misc/consul_rexec_exec.rb

@@ -59,7 +59,8 @@ class MetasploitModule < Msf::Exploit::Remote
           return Exploit::CheckCode::Safe
         end
       rescue JSON::ParserError
-        fail_with(Failure::Unknown, 'Failed to parse JSON output.')
+        vprint_error("Failed to parse JSON output.")
+        return Exploit::CheckCode::Unknown
       end
     end
     Exploit::CheckCode::Unknown