code: def install(self, xmlpath):
          
          #Before we can install it, we need to make sure that none of the existing
          #installed paths point to the same repo.
          from os import path
          fullpath = path.abspath(path.expanduser(xmlpath))
          if path.isfile(fullpath):
              repo = RepositorySettings(self, fullpath)
              if repo.name.lower() not in self.repositories:
                  self.installed.append(fullpath)
                  self._save_installed()
                  self.archive[repo.name.lower()] = {}
                  self._save_archive()
                  
                  self.repositories[repo.name.lower()] = repo
          else:
              warn("The file {} does not exist; install aborted.".format(fullpath))
docs: Installs the repository at the specified XML path as an additional
          repo to monitor pull requests for.