code: def visit_AugAssign(self, node):
          
          self.generic_visit(node)
          if isinstance(node.target, ast.Name):
              name = node.target.id
              res = combine(node.op,
                            self.result[name],
                            self.result[node.value])
              self.result[name] = self.result[name].union(res)
docs: Update range value for augassigned variables.
  
          >>> import gast as ast
          >>> from pythran import passmanager, backend
          >>> node = ast.parse("def foo(): a = 2; a -= 1")
          >>> pm = passmanager.PassManager("test")
          >>> res = pm.gather(RangeValues, node)
          >>> res['a']
          Interval(low=1, high=2)