Ubuntu 16.04 Software Updater: you stopped checks for updates

Run sudo pip3 install --upgrade pip setuptools wheel solved the problems. There must be an error because I use both python 3.5 and 3.6. The error must happened after I reinstall some python 3.6 package. Now the software-updater is working again. I got this from github https://github.com/Homebrew/homebrew-core/issues/3078 . There's also chardet package that lost from python 3.5 installation, that cause the package-downloader from update-notifier to crash. So I runsudo pip3 install --upgrade requests that also install chardet. https://stackoverflow.com/questions/31387799/importerror-cannot-import-name-chardet