[Python] Schematron validation with lxml in Python: how to retrieve validation errors?

I'm trying to do some Schematron validation with lxml. For the specific application I'm working at, it's important that any tests that failed the validation are reported back. The lxml documentation mentions the presence of the validation_report property object. I think this should contain the info I'm looking for, but I just can't figure out how work with it. Here's some example code that demonstrates my problem (adapted from http://lxml.de/validation.html#id2; tested with Python 2.7.4):

import StringIO
from lxml import isoschematron
from lxml import etree

def main():

# Schema
f = StringIO.StringIO('''\
<schema xmlns="http://purl.oclc.org/dsdl/schematron" >
<pattern id="sum_equals_100_percent">
<title>Sum equals 100%.</title>
<rule context="Total">
<assert test="sum(//Percent)=100">Sum is not 100%.</assert>
</rule>
</pattern>
</schema>
''')

# Parse schema
sct_doc = etree.parse(f)
schematron = isoschematron.Schematron(sct_doc, store_report = True)

# XML to validate - validation will fail because sum of numbers
# not equal to 100
notValid = StringIO.StringIO('''\
<Total>
<Percent>30</Percent>
<Percent>30</Percent>
<Percent>50</Percent>
</Total>
''')
# Parse xml
doc = etree.parse(notValid)

# Validate against schema
validationResult = schematron.validate(doc)

# Validation report (assuming here this is where reason
# for validation failure is stored, but perhaps I'm wrong?)
report = isoschematron.Schematron.validation_report

print("is valid: " + str(validationResult))
print(dir(report.__doc__))

main()


Now, from the value of validationResult I can see that the validation failed (as expected), so next I would like to know why. The result of the second print statement gives me:

['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__
format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__get
slice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mo
d__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__',
'__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook
__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center',
'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index
', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper',
'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', '
rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', '
strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']


Which is about as far as I'm getting, based on the documentation and this related question. Could well be something really obvious I'm overlooking?

Continue reading...