verify virtualenv version before installing subcommand (#649)
verify virtualenv version before installing subcommand (#649)
mesosphere/dcos-cli,dcos/dcos-cli,dcos/dcos-cli,mesosphere/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,sis-tools/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,sis-tools/dcos-cli,sis-tools/dcos-cli,kensipe/dcos-cli,mesosphere/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli