fix kerberos tests

Author: baileympearson

src/cmap/connect.ts

@@ -169,17 +169,14 @@ export async function performInitialHandshake(
 
     try {
       await provider.auth(authContext);
-    } catch (cause) {
-      // If we encounter an error authenticating a connection, do NOT apply backpressure labels.
-
-      const error =
-        cause instanceof MongoError
-          ? cause
-          : new MongoRuntimeError('unexpected error during authentication', cause);
+    } catch (error) {
+      // NOTE: If we encounter an error authenticating a connection, do NOT apply backpressure labels.
 
-      error.addErrorLabel(MongoErrorLabel.HandshakeError);
-      if (needsRetryableWriteLabel(error, response.maxWireVersion, conn.description.type)) {
-        error.addErrorLabel(MongoErrorLabel.RetryableWriteError);
+      if (error instanceof MongoError) {
+        error.addErrorLabel(MongoErrorLabel.HandshakeError);
+        if (needsRetryableWriteLabel(error, response.maxWireVersion, conn.description.type)) {
+          error.addErrorLabel(MongoErrorLabel.RetryableWriteError);
+        }
       }
 
       throw error;