Auto merge of #7716 - ehuss:disable-pub-priv-test, r=alexcrichton

[beta] Disable test not forwards compatible to nightly.

The `--extern` flag format changed (see #7699).  The changes didn't make it into beta, so just disable this test.  This isn't immediately necessary, but will be helpful if we need to make any other changes on the 1.41 branch in the future.

Closes #7714

tests/testsuite/pub_priv.rs

@@ -4,6 +4,7 @@ use cargo_test_support::registry::Package;
 use cargo_test_support::{is_nightly, project};
 
 #[cargo_test]
+#[ignore] // Not working on nightly https://github.com/rust-lang/cargo/issues/7714.
 fn exported_priv_warning() {
     if !is_nightly() {
         return;