Hi I had the same Issue, I'm using CentOS 6.8
I did a workaround (Is not the best solution but it works). This happens because for some reason scl is not working properly.
To solve it:
1- First install python requirements
$yum install epel-release
$rpm -ivh
https://rhel6.iuscommunity.org/ius-release.rpmyum --enablerepo=ius install git python27 python27-devel python27-pip python27-setuptools python27-virtualenv -y
2- Workaround for missing files
$ echo /opt/rh > /etc/scl/prefixes/python27
$mkdir /opt/rh/python27
$touch /opt/rh/python27/enable
This solve for me the problem with the
Unable to open: /etc/scl/prefixes/pythonThen i got another problem
virtualenv not found, this can be solved using symbolink link
$cd /usr/bin
$ln -s virtualenv-2.7 virtualenv
I hope this work for you too.