foo.py

from __future__ import unicode_literals

from xml.etree.ElementTree import Element
from xml.etree.ElementTree import SubElement
from xml.etree.ElementTree import tostring


def _build_customer_payload(customer):
    """
    <customer xmlns="http://www.vmware.com/UM">
        <name>Customer Name</name>
        <country>US</country>
        <postalCode>90210</postalCode>
    </customer>

    """
    if not 'country' in customer:
        raise MissingProperty("Missing required 'country'.")
    if not 'name' in customer:
        raise MissingProperty("Missing required 'name'")
    if not 'postal_code' in customer:
        raise MissingProperty("Missing required 'postal_code'")

    attribs = {
        'xmlns': 'http://www.vmware.com/UM'
    }
    root = Element('customer', attribs)
    name = SubElement(root, 'name')
    name.text = customer['name']
    country = SubElement(root, 'country')
    country.text = customer['country']
    postal = SubElement(root, 'postalCode')
    postal.text = customer['postal_code']
    return tostring(root)

###################
# Method from my test

    def test_customer_builder(self):
        customer = {
            'country': 'US',
            'name': '¿Cómo',
            'postal_code': '78555'
        }
        xml = customers._build_customer_payload(customer)
        self.assertIsInstance(xml, str)

ERROR: test_customer_builder (tests.customer_tests.CustomerTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/errr/programs/python/thunderhead/tests/customer_tests.py", line 139, in test_customer_builder
    xml = customers._build_customer_payload(customer)
  File "/Users/errr/programs/python/thunderhead/thunderhead/builder/customers.py", line 114, in _build_customer_payload
    return tostring(root).decode(encoding='utf-8', errors='ignore')
  File "/usr/local/Cellar/python/2.7.8/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 1126, in tostring
    ElementTree(element).write(file, encoding, method=method)
  File "/usr/local/Cellar/python/2.7.8/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 820, in write
    serialize(write, self._root, encoding, qnames, namespaces)
  File "/usr/local/Cellar/python/2.7.8/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 939, in _serialize_xml
    _serialize_xml(write, e, encoding, qnames, None)
  File "/usr/local/Cellar/python/2.7.8/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 937, in _serialize_xml
    write(_escape_cdata(text, encoding))
  File "/usr/local/Cellar/python/2.7.8/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 1073, in _escape_cdata
    return text.encode(encoding, "xmlcharrefreplace")
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 0: ordinal not in range(128)