This solves the error occuring installing python2 softwares:

    error: find_namespace: directive is unsupported on Python < 3.3
    An error occurred when trying to install pyrsistent 0.14.5. Look above this message for any errors that were output by easy_install.
    While:
      Updating slapos-cookbook-dependencies.
      Getting distribution for 'pyrsistent==0.14.5'.