Add deprecation warning for nutils.SI, nutils.unit

Author: gertjanvanzwieten

src/nutils/SI.py

@@ -125,7 +125,9 @@
 import typing
 import numpy
 from functools import partial, partialmethod, reduce
-from . import function, topology, sample
+from . import function, topology, sample, warnings
+
+warnings.deprecation("nutils.SI is deprecated and will be removed in Nutils 11; please use the externally installable nutils.units instead (pip install nutils-units)")
 
 
 class DimensionError(TypeError):

src/nutils/unit.py

@@ -39,6 +39,9 @@
 '''
 
 import re
+from . import warnings
+
+warnings.deprecation("nutils.unit is deprecated and will be removed in Nutils 11; please use the externally installable nutils.units instead (pip install nutils-units)")
 
 
 def create(_typename='unit', **units):