docker: fix python 3.4 error
docker: fix python 3.4 error

TypeError: the JSON object must be str, not 'bytes'

see also: https://stackoverflow.com/questions/6862770/python-3-let-json-object-accept-bytes-or-let-urlopen-output-strings

thc202/zaproxy,kingthorin/zaproxy,psiinon/zaproxy,meitar/zaproxy,zaproxy/zaproxy,Ali-Razmjoo/zaproxy,kingthorin/zaproxy,thc202/zaproxy,gmaran23/zaproxy,psiinon/zaproxy,zapbot/zaproxy,meitar/zaproxy,psiinon/zaproxy,zapbot/zaproxy,psiinon/zaproxy,gmaran23/zaproxy,thc202/zaproxy,gsavastano/zaproxy,psiinon/zaproxy,gmaran23/zaproxy,gsavastano/zaproxy,meitar/zaproxy,gmaran23/zaproxy,thc202/zaproxy,meitar/zaproxy,zaproxy/zaproxy,meitar/zaproxy,Ali-Razmjoo/zaproxy,zaproxy/zaproxy,meitar/zaproxy,meitar/zaproxy,kingthorin/zaproxy,gmaran23/zaproxy,Ali-Razmjoo/zaproxy,zaproxy/zaproxy,gsavastano/zaproxy,psiinon/zaproxy,Ali-Razmjoo/zaproxy,Ali-Razmjoo/zaproxy,Ali-Razmjoo/zaproxy,kingthorin/zaproxy,gmaran23/zaproxy,kingthorin/zaproxy,gsavastano/zaproxy,thc202/zaproxy,kingthorin/zaproxy,zaproxy/zaproxy,zapbot/zaproxy,zaproxy/zaproxy,zapbot/zaproxy,meitar/zaproxy,thc202/zaproxy,gsavastano/zaproxy,zaproxy/zaproxy,gmaran23/zaproxy,gsavastano/zaproxy,gsavastano/zaproxy,zapbot/zaproxy,zapbot/zaproxy,kingthorin/zaproxy,Ali-Razmjoo/zaproxy,zapbot/zaproxy,psiinon/zaproxy,thc202/zaproxy