add error message

Author: ScottWryyyyy

src/main/java/com/alipay/global/api/BaseAlipayClient.java

@@ -135,7 +135,7 @@ private String genSignValue(String httpMethod, String path, String clientId, Str
         try {
             signatureValue = SignatureTool.sign(httpMethod, path, clientId, requestTime, reqBody, merchantPrivateKey);
         } catch (Exception e) {
-            throw new AlipayApiException(e);
+            throw new AlipayApiException("generate signature error", e);
         }
         return signatureValue;
     }
@@ -144,7 +144,7 @@ private boolean checkRspSign(String httpMethod, String path, String clientId, St
         try {
             return SignatureTool.verify(httpMethod, path, clientId, responseTime, rspBody, rspSignValue, alipayPublicKey);
         } catch (Exception e) {
-            throw new AlipayApiException(e);
+            throw new AlipayApiException("verify signature error", e);
         }
     }