I upgraded to symfony 3.4.0-BETA4 by updating composer.json and replacing changes files according to symfony-standard repository.

Everything goes well except the php bin/console cache:clear --no-warmup constantly fails with this error:

 // Clearing the cache for the dev environment with debug true

In Filesystem.php line 181:

  Failed to remove directory "/path/to/my/project/var/cache/de~/ContainerWocmr4b": Undefined variable: lightTrace.

So there is an undefined variable in the debug component.
The actually error is:

"Failed to remove directory "/path/to/my/project/var/cache/de~/ContainerWocmr4b": rmdir(/path/to/my/project/var/cache/de~/ContainerWocmr4b): Directory not empty."

Even I manually rm all the cache folders on cli and still getting this.

btw I'm using Macos 10.13.1 and vagrant nfs shared folder to ubuntu 16.04.3 vbox. command is ran in vbox. php 7.1.13