support newer version of statsmodels

See https://github.com/statsmodels/statsmodels/blob/v0.13.5/statsmodels/tsa/arima_model.py#L6-L12

setup.py

@@ -11,7 +11,7 @@ for f in sorted(glob.glob(os.path.join('slapos', 'README.*.rst'))):
 
 long_description += open("CHANGES.txt").read() + "\n"
 
-prediction_require = ['statsmodels', 'scipy', 'pandas']
+prediction_require = ['statsmodels>=0.11.0', 'scipy', 'pandas']
 test_require = ['mock', 'cryptography', 'websockets; python_version>="3"',] + prediction_require
 
 setup(name=name,

slapos/promise/plugin/check_free_disk_space.py

@@ -22,7 +22,7 @@ from contextlib import closing
 try:
   import pandas as pd
   import numpy as np
-  from statsmodels.tsa.arima_model import ARIMA
+  from statsmodels.tsa.arima.model import ARIMA
 except ImportError:
   pass