Thanks for heads up, looks like updated client broke CentOS 6 + python2.7 IUS Community installed python 2.7
Creating virtual environment...
./letsencrypt-auto: line 167: virtualenv: command not found
relevant section
DeterminePythonVersion
echo "Creating virtual environment..."
if [ "$VERBOSE" = 1 ] ; then
virtualenv --no-site-packages --python $LE_PYTHON $VENV_PATH
else
virtualenv --no-site-packages --python $LE_PYTHON $VENV_PATH > /dev/null
fi
ah problem at my end as my sed match doesn’t match anymore 
sed -i "s|--python python2|--python python2.7|" letsencrypt-auto
or the path to virtualenv not found
rpm -ql python27-virtualenv | grep bin
/usr/bin/virtualenv-2.7
issue submitted https://github.com/letsencrypt/letsencrypt/issues/2300