install incremental before Twisted

Author: gkirok

install

@@ -49,6 +49,7 @@ def main():
         # "python -m pip install" instead of "pip install" handles a pip
         # issue where it fails in a long-named dir
         run('virtualenv venv && source venv/bin/activate && '
+            'python -m pip install {0} incremental && '.format(local_pip_packages) +
             'python -m pip install {0} -r requirements.txt'.format(
                 local_pip_packages))