title: selenium simple test says xpath is not a legal expression
body: <p>I started using SST (selenium simple test) but ran into a problem when executing what seems to be a valid xpath expression <code>'//div[div@data-type="folder-name"]'</code>. SST fails with the following traceback:</p>
  
  <pre><code>Traceback (most recent call last):
  
  File "/usr/local/lib/python2.7/dist-packages/sst/cases.py", line 207, in run_test_script exec self.code in self.context
  File "./sst-one.py", line 7, in &lt;module&gt; names = get_elements_by_xpath('//div[div@data-type="folder-name"]')
  File "/usr/local/lib/python2.7/dist-packages/sst/actions.py", line 1344, in &gt;get_elements_by_xpath_raise(msg)
  File "/usr/local/lib/python2.7/dist-packages/sst/actions.py", line 118, in _raise raise AssertionError(msg)
  AssertionError: Element not found: Message: u'The given selector //div[div@data-&gt;type="folder-name"] is either invalid or does not result in a WebElement. The following &gt;error occurred:\nInvalidSelectorError: Unable to locate an element with the xpath &gt;expression //div[div@data-type="folder-name"] because of the following &gt;error:\n[Exception... "The expression is not a legal expression."  code: "12" nsresult: &gt;"0x805b0033 (SyntaxError)"  location: "file:///tmp/tmp12zCta/extensions/fxdriver@googlecode.com/components/driver_component.js&gt; Line: 5916"]' ;
  Stacktrace: 
      at FirefoxDriver.annotateInvalidSelectorError_ (file:///tmp/tmp12zCta/extensions/fxdriver@googlecode.com/components/driver_component.js:8873)
      at FirefoxDriver.prototype.findElementsInternal_ (file:///tmp/tmp12zCta/extensions/fxdriver@googlecode.com/components/driver_component.js:8931)
      at FirefoxDriver.prototype.findElements file:///tmp/tmp12zCta/extensions/fxdriver@googlecode.com/components/driver_component.js:8935)
      at DelayedCommand.prototype.executeInternal_/h file:///tmp/tmp12zCta/extensions/fxdriver@googlecode.com/components/command_processor.js:10840)
      at DelayedCommand.prototype.executeInternal_ (file:///tmp/tmp12zCta/extensions/fxdriver@googlecode.com/components/command_processor.js:10845)
      at DelayedCommand.prototype.execute/&lt; file:///tmp/tmp12zCta/extensions/fxdriver@googlecode.com/components/command_processor.js:10787)
  </code></pre>
  
  <p>The SST code line is:</p>
  
  <pre><code>names = get_elements_by_xpath('//div[div@data-type="folder-name"]')
  </code></pre>
  
  <p>If I run the same xpath statement using selenium (from python), not SST, it is a valid expression and returns the matching elements if there were any.</p>
  
  <p>The pure selenium code line (where br is the firefox webdriver object) is:</p>
  
  <pre><code>elems = br.find_elements_by_xpath("//div[div/@data-type='folder-name']")
  </code></pre>
  
  <p>I understand this is a bit in the weeds, so if anyone has some hints as to how to debug the .js code that selenium creates in the /tmp directory that would be a big help.</p>