Exception when building xpath query

[t8y8]

I managed to trigger this when downloading workbooks from alpo.

This was done against the HEAD of a local copy of #45

`Traceback (most recent call last):
File "/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/xml/etree/ElementPath.py", line 263, in iterfind
selector = _cache[cache_key]
KeyError: (".//metadata-record[@Class='column'][local-name='[Today's Date]']", None)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "runner.py", line 30, in
fields = wb_model.datasources[0].fields
File "/Users/tdoyle/Documents/py/document-api-python/tableaudocumentapi/datasource.py", line 135, in fields
self._fields = self._get_all_fields()
File "/Users/tdoyle/Documents/py/document-api-python/tableaudocumentapi/datasource.py", line 141, in _get_all_fields
return collections.OrderedDict([(k, v) for k, v in column_objects])
File "/Users/tdoyle/Documents/py/document-api-python/tableaudocumentapi/datasource.py", line 141, in
return collections.OrderedDict([(k, v) for k, v in column_objects])
File "/Users/tdoyle/Documents/py/document-api-python/tableaudocumentapi/datasource.py", line 140, in
for xml in self._datasourceTree.findall('.//column'))
File "/Users/tdoyle/Documents/py/document-api-python/tableaudocumentapi/datasource.py", line 17, in _mapping_from_xml
metadata_record = root_xml.find(xpath)
File "/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/xml/etree/ElementTree.py", line 649, in find
return self._root.find(path, namespaces)
File "/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/xml/etree/ElementPath.py", line 298, in find
return next(iterfind(elem, path, namespaces), None)
File "/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/xml/etree/ElementPath.py", line 277, in iterfind
selector.append(ops[token[0]](next, token))
File "/usr/local/Cellar/python3/3.5.1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/xml/etree/ElementPath.py", line 233, in prepare_predicate
raise SyntaxError("invalid predicate")
SyntaxError: invalid predicate`

[t8y8]

Looks like values can't have quotes for xpath in python.

From the docs: Selects all elements for which the given attribute has the given value. The value cannot contain quotes.

https://docs.python.org/3/library/xml.etree.elementtree.html#supported-xpath-syntax

[graysonarts]

Yup, I saw that when I was developing the xpath, but can't believe we don't encode the quote when writing out to the xml. I'll have to check for single quotes and revert to a more expensive search to get around this. I'll get this fixed in the morning. Can you send me the file where you ran into this? I'll turn it into a test case (after cleaning up any potential private information from it, of course)

[t8y8]

I found the twb (I'll send it to you offline until we can scrub it)

We do actually encode it: '[Today's Date]'

[graysonarts]

hah when I looked at that, it didn't include the & code and I was like "How is that even possible?" Okay so I'll need to add encoding step specifically for 's