se adiciona FachoXml.get_element_attribute para obtener atributo de xpath

FossilOrigin-Name: b3be980dca00b8bd117c4a7e176b8d3a9bac804a1200ad4b7cc39e0f4ab0be15

facho/facho.py

@@ -104,6 +104,9 @@ class LXMLBuilder:
     def get_text(self, elem):
         return elem.text
 
+    def get_attribute(self, elem, key):
+        return elem.attrib[key]
+
     def set_attribute(self,  elem, key, value):
         elem.attrib[key] = value
 
@@ -276,6 +279,10 @@ class FachoXML:
             self.builder.set_attribute(elem, k, v)
         return self
 
+    def get_element_attribute(self, xpath, attribute):
+        elem = self.get_element(xpath)
+        return self.builder.get_attribute(elem, attribute)
+
     def get_element(self, xpath):
         xpath = self.fragment_prefix + self._path_xpath_for(xpath)
         return self.builder.xpath(self.root, xpath)