Move assert code.

Author: gannan08

lib/KmsClient.js

@@ -692,6 +692,7 @@ export class KmsClient {
       capability = `${ZCAP_ROOT_PREFIX}${encodeURIComponent(url)}`;
     }
 
+    let result;
     try {
       const headers = await signCapabilityInvocation({
         url, method: 'post', headers: DEFAULT_HEADERS, json: config,
@@ -700,19 +701,19 @@ export class KmsClient {
 
       const agent = httpsAgent || this.agent;
       // send request
-      const result = await httpClient.post(url, {
+      result = await httpClient.post(url, {
         agent, headers, json: config
       });
-
-      _assert(result.data, 'result.data', 'object');
-      _assert(result.data.id, 'result.data.id', 'string');
-      return result.data;
     } catch(e) {
       _handleClientError({
         message: 'Error during "create keystore" operation.',
         cause: e
       });
     }
+
+    _assert(result.data, 'result.data', 'object');
+    _assert(result.data.id, 'result.data.id', 'string');
+    return result.data;
   }
 
   async _getUncachedKeyDescription({url, capability, invocationSigner}) {