cloudflare_dns: fix KeyError (#243)

Fix errors of the type KeyError: 'success' to show a more meaningful message

Fixes: #236

changelogs/fragments/243-cloudflare_dns_fix_keyerror.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - cloudflare_dns - fix KeyError 'success' (https://github.com/ansible-collections/community.general/issues/236).

plugins/modules/net_tools/cloudflare_dns.py

@@ -496,6 +496,10 @@ class CloudflareAPI(object):
         if result is None:
             self.module.fail_json(msg=error_msg)
 
+        if 'success' not in result:
+            error_msg += "; Unexpected error details: {0}".format(result.get('error'))
+            self.module.fail_json(msg=error_msg)
+
         if not result['success']:
             error_msg += "; Error details: "
             for error in result['errors']: