Comment # 1 on bug 1045886 from Roger Whittaker

I believe the problem here is related to systemd.

Previously I found that simply downgrading the kernel had no effect on this
problem.  And there had been no change in the version of ecryptfs-utils.

But after forcing a downgrade to systemd-232-10.2, now I see success:

$ ecryptfs-setup-private 
Enter your login passphrase [roger]: 
Enter your mount passphrase [leave blank to generate one]: 

************************************************************************
YOU SHOULD RECORD YOUR MOUNT PASSPHRASE AND STORE IT IN A SAFE LOCATION.
  ecryptfs-unwrap-passphrase ~/.ecryptfs/wrapped-passphrase
THIS WILL BE REQUIRED IF YOU NEED TO RECOVER YOUR DATA AT A LATER TIME.
************************************************************************


Done configuring.

Testing mount/write/umount/read...
Inserted auth tok with sig [38016f72d097f6f6] into the user session keyring
Inserted auth tok with sig [a6db1a352f8f2d14] into the user session keyring
Inserted auth tok with sig [38016f72d097f6f6] into the user session keyring
Inserted auth tok with sig [a6db1a352f8f2d14] into the user session keyring
Testing succeeded.

Logout, and log back in to begin using your encrypted directory.