core: Check STATUS_FAILURE in export operations.

* src/export.c (op_data_t): Add failure_code.
(export_status_handler): Set it.
(gpgme_op_export_ext, gpgme_op_export_keys): Also check the failure
code.
--

That is just in case we missed an error code.  For example with older
gpg versions (e.g. 2.3.8) and exporting to a keyserver.

src/export.c

@@ -35,7 +35,12 @@
 /* Local operation data.  */
 typedef struct
 {
-  gpg_error_t err;  /* Error encountered during the export.  */
+  /* The error code from a FAILURE status line or 0.  */
+  gpg_error_t failure_code;
+
+  /* Error encountered during the export.  */
+  gpg_error_t err;
+
 } *op_data_t;
 
 
@@ -110,6 +115,10 @@ export_status_handler (void *priv, gpgme_status_code_t code, char *args)
         opd->err = err;
       break;
 
+    case GPGME_STATUS_FAILURE:
+      opd->failure_code = _gpgme_parse_failure (args);
+      break;
+
     default:
       break;
     }
@@ -356,7 +365,7 @@ gpgme_op_export_ext (gpgme_ctx_t ctx, const char *pattern[],
           err = _gpgme_op_data_lookup (ctx, OPDATA_EXPORT, &hook, -1, NULL);
           opd = hook;
           if (!err)
-            err = opd->err;
+            err = opd->err ? opd->err : opd->failure_code;
         }
     }
 
@@ -501,7 +510,7 @@ gpgme_op_export_keys (gpgme_ctx_t ctx,
           err = _gpgme_op_data_lookup (ctx, OPDATA_EXPORT, &hook, -1, NULL);
           opd = hook;
           if (!err)
-            err = opd->err;
+            err = opd->err ? opd->err : opd->failure_code;
         }
     }