esx: Report an error when auth pointer is missing instead of declining

Otherwise an attempt to use virConnectOpen or virConnectOpenAuth without
auth pointer results in the driver declining the URI and libvirt falling
back to the remote driver for an esx:// URI.

src/esx/esx_driver.c

@@ -922,9 +922,18 @@ esxOpen(virConnectPtr conn, virConnectAuthPtr auth, int flags ATTRIBUTE_UNUSED)
         return VIR_DRV_OPEN_DECLINED;
     }
 
-    /* Decline URIs without server part, or missing auth */
-    if (conn->uri->server == NULL || auth == NULL || auth->cb == NULL) {
-        return VIR_DRV_OPEN_DECLINED;
+    /* Require server part */
+    if (conn->uri->server == NULL) {
+        ESX_ERROR(VIR_ERR_INVALID_ARG, "%s",
+                  _("URI is missing the server part"));
+        return VIR_DRV_OPEN_ERROR;
+    }
+
+    /* Require auth */
+    if (auth == NULL || auth->cb == NULL) {
+        ESX_ERROR(VIR_ERR_INVALID_ARG, "%s",
+                  _("Missing or invalid auth pointer"));
+        return VIR_DRV_OPEN_ERROR;
     }
 
     /* Allocate per-connection private data */