Software & Updates (software-properties-gtk): 'EOFError: marshal data too short'

I cannot open Software & Updates tool on 14.04 and get the following error:

Here is the full output of apt-get update, it shows this warning:

W: GPG error: Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 99E82A75642AC823 

When I run sudo software-properties-gtk, I get this error traceback. It shows errors like EOFError: marshal data too short.

How can I fix this?

2 Answers

There are two problems:

• GPG missing key error on the repository
• EOFError: marshal data too short when Python3 tries to import urllib to launch software-properties-gtk (the "Software & Updates" settings window)

To resolve the GPG error, please follow @GAD3R's answer or any answer to How do I fix the GPG error "NO_PUBKEY"?

You decided to remove this repository from your software sources, which is also ok if you don't need it any more.

To resolve the Python EOFError, we need to eliminate some *.pyc files. Those are compiled byte code of a script, which gets dynamically created when a Python script runs to speed up future launches. They are faulty and don't match the original script any more for whatever reason. We can simply delete them as they are not really needed and will be recreated on the next launch.

We don't want a massacre but a small and effective removal of the faulty files only. Therefore we look at the error traceback from the software-properties-gtk output and find out that this error always happens when Python 3.4 tries to import urllib.parse. To avoid follow-up errors we simply remove all *.pyc files related to Python 3.4's urllib module:

sudo rm -r /usr/lib/python3.4/urllib/__pycache__ 

Type the following command :

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 99E82A75642AC823 sudo apt-get update