This should do it, though I haven't tested it
Code:
needs_subscription = 'optional'
def get_browser(self):
br = BasicNewsRecipe.get_browser(self)
if self.username is not None and self.password is not None:
br.open('http://dilemaveche.ro/user/login')
br.select_form(nr=0)
br['username'] = self.username
br['password'] = self.password
br.submit()
return br