from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
buf = StringIO.StringIO()
config_source = "my cloud-config text read from file"
multi_part_mime = MIMEMultipart()
part = MIMEText(config_source, 'cloud-config')
multi_part_mime.attach(part)
buf.write(multi_part_mime.as_string())
userdata = buf.getvalue()
novaconn.servers.create(... userdata=userdata)